ENH: Simplify marching_cubes for maintainability.

This does not change execution time, but the entire algorithm
is much simpler to read and understand without the branching
Cython code paths for anisotropic inputs. Memory usage decreases
a minor amount.
Fix #1108
Merge pull request #1124 from blink1073/master

Fix import when not built (closes gh-1108)
Fix matplotlib install, make installs verbose, add spacers
Fix typo in spacer declaration
Merge pull request #1128 from blink1073/fix-travis

Fix travis build for python 3.2
Add mask option to exposure.equalize_hist with test.

Remove print and fix comparision to None

Update test to make it clear there is a difference

Fix mask logic and `equalize_hist` in `__all__`.

Fix handling of mask and tweak mask test

Another run at travis

Update travis to avoid conflict
Merge pull request #1109 from blink1073/add-exposure-mask

Add mask option to exposure.equalize_hist with test.
Speedup moments_central function
Speedup moments function
Make moments functions C functions and reuse centralized moments
Replace pow() with iterative multiplication
Merge pull request #1096 from ahojnnes/regionprops-speedup

Speed up image moments and and central moments computation.
Remove leftovers of old logger
Merge pull request #1115 from JDWarner/enh_marching_cubes

ENH: Simplify `marching_cubes` for maintainability
Merge pull request #1129 from stefanv/log_leftovers

Remove leftovers of old logger