Split chemkin.loadChemkinFile into smaller functions.

I have made a readSpeciesBlock and readThermoBlock just like
the existing readReactionsBlock.
This is so you can call them independently, should you need to.
Chemkin thermo parser reads more detailed info.

It now extracts the comment, checks the phase, and extracts
the chemical formula.

* readThermoEntry returns (name, thermo, formula) whereas before
it was just (name, thermo).
* readThermoBlock now returns a dictionary of formulae, whereas
before it didn't return anything.

The formula is a dictionary of (element: number) pairs, like
{'C':2, 'H':6}
A standalone script convertThermo.py for making Thermo Library files.

This is to read in somebody's chemkin file, and turn it into a thermo library.
Eventually this should help you identify what the species are, but it doesn't
do that quite yet.
Help constructing SMILES strings when converting thermo files.