Fix includes
Merge branch 'master' of github.com:timvdm/Helium
Fix in Depict for aromatic rings
Add unit test for masked ordered DFS
Forgot data file...
Update python invariants test for added bon order sum atom invariant
Update data files for updated canonicalization
Optimize extented_connectivities()
Optimize canonicalization further
Comment out debug statements in isomorphism.h
Start replacing exceptions in file I/O with error() functions.
Add more debug info to fingerprints unit tests