REF: reorganize pandas/tests/test_series.py
Similar to test_frame.py, but only 8K lines to deal with this time. 

The sparse tests were relying on a small subset of unit tests in `CheckNameIntegration` (including several tests which didn't use non-sparse Series at all). I'll fix this up in the next day or two to get the build passing so this doesn't linger too long
 @jreback Think I fixed the sparse tests, merge away after review when ready
 thanks!
