FEAT: Fuzzy C-Means prediction (for independent test data)

This PR adds predictive capability to the Fuzzy C-Means clustering
algorithm. Now, users can cluster data using `cmeans` and then
input independent test data; a new fuzzy c-membership matrix will
be generated with the membership of each point in known clusters.

Further API changes and cleanup are likely, but the functionality
will remain.
Merge pull request #11 from JDWarner/add_cmeans_prediction

FEAT: Fuzzy C-Means prediction (for independent test data)