In classifier.py: ========================================================

- Renamed functions to better reflect their purpose/scope.
- Simplified procedure for obtaining the final decision table. Some
matrix operations weren't really necessary since the score for
0-output label is always K - (score for 1-outpu label) where K
is the sum of weights.
- Added tests for some functions.

In classifier_example.py
========================================================

- Renamed function calls, according to changes detailed above.
- There is no need to reload the xpl files, since we can copy
the frequency data before doing the iterations.