Updated harmonic_oscillators.py tests to eliminate pandas dependency and support both u_kln and u_kn formats.
Eliminated pandas requirements from setup.py and requirements.txt.
Converted exponential tests.
Removed matplotlib from requirements.txt
Fixed doctests.
Renamed exponential_averaging.py to exp.py
Removed pandas-dependent conversion code.  (Sorry!)
Fixed nosetests.
Fixed issue with EXP import.
Merge pull request #54 from jchodera/master

Unifying tests for pymbar-2.1