TEST: added skips to make the tests more readable
PEP 8
Removed prints and del
TEST: Removed all the prints from test_optimize
Merge pull request #482 from Garyfallidis/fix_optimize_defaults_skip

TST: Skip tests for different versions of scipy for optimize.py
RF: deleted unused files
Merge pull request #485 from Garyfallidis/clean_eit

RF: deleted unused files
BF: fix travis version setting

Luckily Steven Silvester noticed that selecting Python versions for the
virtualenvs was not working : https://github.com/nipy/dipy/issues/487
Merge pull request #488 from matthew-brett/fix-travis-again

BF: fix travis version setting
NF: unique rows of an array.
NF: Added a crutch function. This will need to be removed later on.

And replaced with `move_streamlines`, but I am defering that until I get a
sense of what is happening here.
NF: Added a first-pass implementation of LiFE.
RF: Thinking about simplifying this.

Maybe use dipy.sims.voxel directly?
WIP: Completed the mapping function voxel2fiber, inclduing test.
Matrix allocation more-or-less working.
WIP: Still working out how to create this model.
NF: Added Sparse SGD algorithm for solution of the LiFE equations.
TST + BF: Make sure that input to np.gradient is an array.
RF: Move down the fit function.
RF: docs