added two tests
changed a datatype setting when building the visuotopic coordinate matrices
NF: Added some normalization functions to the utilities.
RF: Use flexible normalization (whatever users choose).

Also some PEP8 of some variable names.
RF: Just a suggestion for this problem.
PEP8: just some white-space.
RF: tried clarifying this a bit.

Did I get it all right?
TST: Moved this into a module-specific testing file.
DOCS: A little bit of documentation, and a lot of line-wrapping.
BF: Add the (crucial) 1D case to zscore.
Changed `testing` into `test_spinach`, so that we have more granularity.
RF: First pass at separating out the single voxel case from estimation.

Trying to break down the long function `compute_prf_estimate` and make it
easier to use (?).
Merge pull request #5 from arokem/faces

Faces