homogenize some test-ish code. source lives in testproject. inherit from pants-int

some of our code-meant-for-testing was in 'examples', some was in 'testproject'.
mv */examples/unicode -> */testproject/unicode

add integration tests to exercise commands that have revealed regressions before

Testing Done:
./build-support/bin/ci.sh

Reviewed at https://rbcommons.com/s/twitter/r/508/
Add support for multiple pants_support_baseurls.

Changed pants_support_baseurl to a list. Pants now goes through each url in the list from first to last, downloading the first binary with a valid url (and then breaking). This way, pants users can set their own support repo online and add it to the beginning of the list, so that their repo will be queried before the default repo on pantsbuild.github.io.