TST: add some basic tests for the FetchAPI class.
TST: test fetch api when using encore progress bar.
DOC: document a bit what MockedFailingFile does.
TST: ensure we actually use the progress manager in fetch.
STY: remove the os.path as op that caused tremoundous incomfort to Mark.
STY: fix ws issues.
REF: use assertRaises context manager.

We're actually already depending on unittest2, so better use it.
Merge pull request #127 from enthought/test_fetch_api

Test fetch api