Added activate method in nnetwork. Tested in nntrainer_test.
Added tests and calculateCost method in nnetwork.
Updated imports.
Added a dimensions attribute to NNetwork.
Replaced nntrainer with a training file. Added util methods.

Generalized several methods that were originally in nntrainer
and nntrainer_test and placed them in the util file. nntrainer is
now not an object anymore and several training methods are now
in the training file.
Updated tests to reflect changes and removed nntrainer_test.
Added a mathutil and moved methods in util to this new file.

util is now a ubiquitous holder for all the utility tools that
pymind uses. These are utility functions, methods, or objects
that are not necessarily related to pymind and neural networks.
Merge remote-tracking branch 'origin/frontend'

Conflicts:
	pymind/util.py
	test/util_test.py