Fix typos (#66)

This is a pull request to correct typos.

Author: kojix2

lib/unicode_plot/barplot.rb

@@ -73,7 +73,7 @@ def print_row(out, row_index)
   #
   #   Draws a horizontal barplot.
   #
-  #   @param text [Array<String>] The lables / captions of the bars.
+  #   @param text [Array<String>] The labels / captions of the bars.
   #   @param heights [Array<Numeric>] The values / heights of the bars.
   #   @param xscale [nil,:log,:ln,:log10,:lg,:log2,:lb,callable]
   #          A function name symbol or callable object to transform the bar

lib/unicode_plot/boxplot.rb

@@ -163,7 +163,7 @@ def print_row(out, row_index)
       name = args[0]
       data = args[1]
     else
-      raise ArgumentError, "worng number of arguments"
+      raise ArgumentError, "wrong number of arguments"
     end
 
     if data.empty?

lib/unicode_plot/scatterplot.rb

@@ -17,7 +17,7 @@ class Scatterplot < GridPlot
       x = Array(args[0])
       y = Array(args[1])
     else
-      raise ArgumentError, "worng number of arguments"
+      raise ArgumentError, "wrong number of arguments"
     end
 
     plot = Scatterplot.new(x, y, canvas, **kw)
@@ -38,7 +38,7 @@ class Scatterplot < GridPlot
       x = Array(args[0])
       y = Array(args[1])
     else
-      raise ArgumentError, "worng number of arguments"
+      raise ArgumentError, "wrong number of arguments"
     end
 
     color = color == :auto ? plot.next_color : color