Added geometric mean to tool.py
This is a step to removing all dependencies on scipy (where possible)
Added two new features.
1. Minimum free energy
2. Ensemble free energy
Slight refactoring of which feature generators can be found in which file
Tweaked the underlying algorithm for the codon adaptation index generator
Improved regular expression for codon usage table parser
Added a method to extract all ORFs from a sequence
Added new feature
1. Number of ORFs in a sequence