Move unimportant prerequisites inside functions and classes where used.

Move unimportant prerequisites such as Fipy, pyFFTW, etc. into the function and classes where they are used. User can import pymks without an error now.

Fix #56
Merge remote-tracking branch 'davidbrough1/issue56-prerequisites'

Fix #56

Conflicts:
	pymks/fastmksRegressionModel.py
	pymks/fipyCHModel.py