Enable HTTP Proxies for iControlRESTTokenAuth

Issues:
Fixes #172

Problem:

The `proxies` attribute is available on the `iControlRESTSession` object,
 however it does not get passed to the `iControlRESTTokenAuth` object.
As a result, if all communication with a BigIP device needs to take place
 via a Proxy, authentication will fail and timeout.
Analysis:

I added `proxies` as a Kwarg on the `iControlRESTTokenAuth` object.
I then passed that argument in from the `iControlRESTSession` object
 instantiations of the `iControlRESTTokenAuth` object.
I then added `proxies=self.proxies` to the two instances of
 `requests.<verb>` in the `iControlRESTTokenAuth` object.
Tests:

I am unable to run the tests as listed in the documentation as even in 1.0 branch,
 `py.test --cov ./ --cov-report=html` returns:
 `argparse.ArgumentError: argument --bigip: conflicting option string: --bigip`

I did successfully test with and without proxies, by installing my fork/branch
 and testing against a live BigIP

With Proxies:

    In [1]: paste
    from f5.bigip import ManagementRoot
    from getpass import getpass
    password = getpass()
    user = "test_user"
    host = "test_f5.local"
    mah_f5 = ManagementRoot(hostname=host, username=user, password=password, proxies={"https": "socks5://127.0.0.1:8000"}, auth_provider="tmos")
    mah_f5.tmos_version

    ## -- End pasted text --
    Password:
    Out[1]: '14.1.2.3'

Without Proxies:

    In [1]: paste
    from f5.bigip import ManagementRoot
    from getpass import getpass
    password = getpass()
    user = "test_user"
    host = "localhost"
    port = 30002
    mah_f5 = ManagementRoot(hostname=host, port=port, username=user, password=password, auth_provider="tmos")
    mah_f5.tmos_version

    ## -- End pasted text --
    Password:
    Out[1]: '14.1.2.3'

Author: lykinsbd

icontrol/authtoken.py

@@ -55,6 +55,8 @@ class iControlRESTTokenAuth(AuthBase):
     BigIP should consult when creating the token.
     :param str verify: The path to a CA bundle containing the \
     CA certificate for SSL validation
+    :param proxies: A dict of proxy information for Requests to utilize \
+    on this connection to the BigIP
 
     If ``username`` is configured locally on the BigIP,
     ``login_provider_name`` should be ``"tmos"`` (default).  Otherwise
@@ -63,10 +65,11 @@ class iControlRESTTokenAuth(AuthBase):
     of ``login_provider_name``.
     """
     def __init__(self, username, password, login_provider_name='tmos',
-                 verify=False, auth_provider=None):
+                 verify=False, auth_provider=None, proxies=None):
         self.username = username
         self.password = password
         self.login_provider_name = login_provider_name
+        self.proxies = proxies
         self.token = None
         self.expiration = None
         self.attempts = 0
@@ -95,7 +98,7 @@ def get_auth_providers(self, netloc):
         """
         url = "https://%s/info/system?null" % (netloc)
 
-        response = requests.get(url, verify=self.verify)
+        response = requests.get(url, verify=self.verify, proxies=self.proxies)
         if not response.ok or not hasattr(response, "json"):
             error_message = '%s Unexpected Error: %s for uri: %s\nText: %r' %\
                             (response.status_code,
@@ -147,7 +150,8 @@ def get_new_token(self, netloc):
             login_url,
             json=login_body,
             verify=self.verify,
-            auth=HTTPBasicAuth(self.username, self.password)
+            auth=HTTPBasicAuth(self.username, self.password),
+            proxies=self.proxies,
         )
         self.attempts += 1
         if not response.ok or not hasattr(response, "json"):

icontrol/session.py

@@ -428,22 +428,22 @@ def __init__(self, username, password, **kwargs):
 
         # Handle token-based auth.
         if token_to_use:
-            self.session.auth = iControlRESTTokenAuth('admin', 'admin')
+            self.session.auth = iControlRESTTokenAuth('admin', 'admin', proxies=proxies)
             self.session.auth.token = token_to_use
         else:
             if auth_provider:
                 self.session.auth = iControlRESTTokenAuth(
-                    username, password, auth_provider=auth_provider, verify=verify
+                    username, password, auth_provider=auth_provider, verify=verify, proxies=proxies
                 )
             else:
                 if token_auth is True:
                     self.session.auth = iControlRESTTokenAuth(
-                        username, password, verify=verify
+                        username, password, verify=verify, proxies=proxies
                     )
                 elif token_auth:
                     # Truthy but not true: non-default loginAuthProvider
                     self.session.auth = iControlRESTTokenAuth(
-                        username, password, token_auth, verify=verify
+                        username, password, token_auth, verify=verify, proxies=proxies
                     )
                 else:
                     self.session.auth = (username, password)