Added the function saveChemkinFileEdge.

This function writes for debugging the molecules in the edge into a
ChemkinFile similar to the function saveChemkinFile for the core
molecules but with additional information.
Added functions to write the edge of the model as CHEMKIN files.
Additional Atom Energies and Bond Additivity Corrections
Exclude radicals with one heavy atom from maxRadicals limitation
Correct the assertion of maximum number of radicals
Add functions to determine if biradical is singlet and is triplet
Addding function changing triplet radical to singlet radical
Function checking reverse reactions of CH2(S) for correct multiplicity
Correct BAC for CCSD(T)-F12/cc-pVTZ-F12 'C-O'
A preliminary solution for the reverse reaction of CH2(T) + CH

Introducing 1-centered biradicals to the H-abstraction family lets RMG
find the special case of CH2(T) + CH = CH + CH2(T). However for the
reverse reaction it recognizes that nothing happens and removes the
reverse reaction from the reaction list which leads an error for empty
reaction lists.
Add function to set spin multiplicity of an atom
Add function getRadicalAtoms to class Molecule

This function returns a list of atoms of the molecules containing at
least one unpaired electron.
limit allyl resonance structure generation to monoradicals
Give the edge CHEMKIN files the same numbering as for the core ones

- this prevents two edge files having the same number of species from
overwriting each other
Added some Cython declarations to molecule.py
Added an isValidMolecule() method to molecule() to detect errors.

Next step is to call this frequently and assert that it is always true.
Perhaps after every reaction makes a molecule.

I also made a unit test to check that it sometimes works.

Warning: This will need changing on the master branch with Nitrogen.
Check for valid molecules after making reactions.

In an ideal bug-free world this check would not be necessary,
Hopefully it does not slow things down much, and is helpful in
detecting problems in reaction recipes.
Hopefully it helps @faribas figure out her current problem.