Write tests for Chart class

Also fixed issue with code calulating the factor which didn't handle
floats correctly sometimes...
Add terminal chart via gnuplot
Fix index-miss example in array, and add termplot
Don't write tests against uncommitted work
Add teal to list of chart colors so orange isn't repeated
Add Ruby version indicator to bottom of chart
Add more document for termplot
Update positioning of labels
Add compare? helper
Add some comments for the data and data_for methods in report
Add termplot tests
Bump up timing tolerance on timing tests that occasionally fail
Merge pull request #12 from davy/termplot

Termplot
Add String generator
Add :size generator
Add new generators to CHANGELOG