Bias Calculation: (O - E) / (O + E)

Use the difference of observation and expected and compares it to the
sum of the corresponding observed and expected. Show direction and
magnitude of change.

Verification:
 1. Run python3 normalized_bias_calculator.py
 2. Check data in SubstitutionAnlysResults.xlsx

Patch Set 2: Add .gitignore
Merge branch 'master' of NormalizedSubstitutionBias

Conflicts:
	.gitignore
Move Normalized Bias Calculations to XlFlexComputer subfolders.