Change size of avatar widget from 1x1 to 2x1
Make avatar image a circle

See: http://webdesignerwall.com/tutorials/css3-image-styles
Set up testing with rspec, webmock
Add test for StackOverflow::fetch yielding nil
Add some tests for StackOverflow request URL patterns
Gracefully fail if no block given to StackOverflow.fetch
Merge branch 'tests'