PEP-8

* Import tidying & sorting (stdlib, third-party, local
* Trailing whitespace removal
NeedleTestCase: refactor driver setup to setUpClass

This saves a considerable amount of time by not loading the driver
for every test (50%+ of runtime with 7 tests with Firefox).
NeedleTestCase: enable baseline capture using environmental variable

This allows running with the standard python unittest2 discovery
or even simple command-line usage rather than nose.