pandas 0.20 compatibility

[bmcfee]

This will be fun. Not sure how deep this all goes, but I think we're in for some compatibility headaches.

In [3]: J = jams.load('trapped.jams')
/home/bmcfee/git/jams/jams/core.py:1852: FutureWarning: pandas.tslib is deprecated and will be removed in a future version.
You can access Timedelta as pandas.Timedelta
  if isinstance(obj, pd.tslib.Timedelta):

[bmcfee]

For reference, here are the release notes.

Running locally, it's a total disaster:

Ran 759 tests in 23.096s

FAILED (failures=271)

[justinsalamon]

😱😱😱

[bmcfee]

It looks like these all(?) stem from the same issue inside JamsFrame.add_observation that is not allowing us to append strings into the value column.

[bmcfee]

Punting upstream to https://github.com/pandas-dev/pandas/issues/16309 , but I don't think we should wait on pandas to fix it for us.