Update test_indexer for pandas 0.13.1 and python 2.7
Update test_note_rest_indexer for pandas 0.13.1 and python 2.7
Update interval.py Tests for pandas 0.13.1 and python 2.7

Includes revisions to the HorizontalIntervalIndexer itself.
Update test_repeat.py for fun
Update ngram.py and Tests for pandas 0.13.1 and python 2.7
Correct test_frequency_experimenter.py for pandas 0.13.1 and Python 2.7

I updated the tests' format, but this actually revealed a deficiency where
not all parts of the DataFrame were being checked, and the "expected" values
were actually wrong.
Update test_workflow.py for pandas 0.13.1
Allow pandas up to 0.14 in requirements.txt

... thus "officially" adding support for pandas 0.13.0 and 0.13.1

closes #273