Add decomposition tests

These tests pass IF you run them one at a time, due to an
existing bug in decomposition with memory mangement. I'm
adding this to ensure no regressions for the next fixes.
Fix a memory management bug

Don't assign back to the passed data matrix!
Using np.sqrt is about 5 times fast than power

Also, always put decimal places for floating point division!
Forgot a decimal point on the power
Add the inplace keyword and update the docstring

Still need to make sure that our PCAModel uses this keyword
by default!
Set inplace kwarg in PCAModel
Merge remote-tracking branch 'upstream/master' into decomposition_fix
Merge pull request #305 from patricksnape/decomposition_fix

Decomposition fix