Make test runner selectable
add dependency to package with test to check that it was installed. Fixes #9
use requirements.txt file to specify dependenies. Fixes #31
Disable colorized Pylint

This was showing up as garbage in my terminal.
Pylint cleanup
make runner selectable by environment variable
use file flag to indicate if chosen test runner is installed
revert test runner flag changes. update README.
Ignore pyunit.xml
Instruct user to remove Travis env lines
Merge pull request #30 from jacebrowning/test-runner-select

Make test runner selectable