ENH: Better method for getting user home folder

mne.utils module attempts to find the user home folder by searching for
the environment variable HOME; however, this is not necessarily
available depending on how the Python program was launched (e.g. via
Upstart).  Switched to a more robust method for identifying the home
folder.
Merge pull request #980 from bburan-galenea/bburan-galenea/env-var-fix

ENH: Better method for getting user home folder
Travis configured for Py3.3
WIP: Better py3k support
ENH: Better write support
Fixes for brainvision and bti test cases
FIX: Fix some writes
FIX: Fix warnings catch
FIX: Fix fix
FIX: Fix some writes
FIX: Fix Py3 STC operators
FIX: Fix reads
STY: PEP8
FIX: Fix divide
FIX: Fix viz
FIX: Fix raw
FIX: Fix raw copy
FIX: Fix cov and utils
FIX: Fix parc
FIX: Travis