Add testing of doctest coverage with --doc-coverage
Add doctest coverage comparison against master
Fix incorrect variable
Fix summary word for doctest coverage
Apply pyflakes fixes to the code base
Compare percentages only for doctest coverage
Use -v in coverage_doctest.py
Add clipart images for doctest coverage

These are either from or based on images from the Tango project
(http://tango.freedesktop.org/Tango_Desktop_Project). Some are remixes from
http://openclipart.org/.  All are public domain.
Crop green up arrow to be same size as red down arrow
Add images to the doctest coverage summary
Remove inconsistent parentheses in doctest coverage summary
Use the arrow symbols for the overall coverage status
Give the report url in the doctest coverage summary again
Fix some bugs
Fix a bug
Use master_name in doctest coverage summary
Include one more digit in the percentages, because there could have been rounding
Compare the actual percentage, not the truncated one
Merge pull request #161 from asmeurer/doctest_coverage

Add testing of doctest coverage with --doc-coverage
Use the sympy url for image hosting

This will probably break soon (see
https://github.com/blog/1482-heads-up-nosniff-header-support-coming-to-chrome-and-firefox).