Revert "Experimenting with import order"

This reverts commit c407a00, which selected the Agg backend for
Matplotlib in pymc/__init__.py, overriding the effects of 40a8070. These
changes were unnecessary to fix the non-interative display errors in the
Travis tests and prevent interactive plotting unless the user has
selected a backend prior to importing pymc.

Author: kyleam

pymc/__init__.py

@@ -1,6 +1,4 @@
 __version__ = "3.0"
-import matplotlib
-matplotlib.use('Agg')
 
 from .core import *
 from .distributions import *