incompatible with latest mdtraj

[dermen]

In [1]: import thor
WARNING:xsdimage:lxml library is probably not part of your python installation: disabling xsdimage format
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-0103ce0c7928> in <module>()
----> 1 import thor

/Users/mender/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/thor/__init__.py in <module>()
      7 
      8 # dump a few things into the THOR namespace
----> 9 from xray import *
     10 
     11 # list all the files included in THOR

/Users/mender/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/thor/xray.py in <module>()
     31 
     32 from mdtraj import io
---> 33 from mdtraj.utils.arrays import ensure_type
     34 
     35 # ------------------------------------------------------------------------------

ImportError: No module named arrays

[dermen]

seems the function ensure_type can be imported directly from`mdtraj.utils```. I committed the patch.

[tjlane]

cool thanks!