Implement hydrogen bond detection

[josemduarte]

It should be straight forward to detect Hydrogen bonds for protein-protein contacts. All the necessary data is already in AICGraph class.

See some papers:

The classic DSSP by Kabsch and Sander: http://onlinelibrary.wiley.com/doi/10.1002/bip.360221211/abstract

From the Thornton group:
http://www.ncbi.nlm.nih.gov/pubmed/8182748

A nice review article:
http://onlinelibrary.wiley.com/doi/10.1002/9780470015902.a0003011.pub2/abstract