Fixed error occuring when pandas is not installed
Merge pull request #51 from nhfechner/master

Potentially fixed error caused by PandasTools if pandas is not installed
Merge branch 'master' of https://github.com/rdkit/rdkit into fmcs_update
Fixes #52
Fixes #54
Fixes #53
Fixes #56
Merge branch 'master' into fmcs_update