Introduced `getNumberDegreesOfFreedom` into conformer class

This partially addressed issue #213.

This function gives the total molecular degrees of freedom for a
species. I think it belongs in the conformer class, but please let me
know if you think otherwise. I've also included a couple unittests for
ethane and ethylene. I've recompiled RMG-Py and ensured that it's
working. That it's working is one thing, but apologies in advance for
the crappy programming style :)

fixup! Introduced `getNumberDegreesOfFreedom` into conformer class

Rather than look up self.conformer.modes[i] loads of times,  we look it up once
and store it in a local variable 'mode'. It is lookups that take time in Python,
so this would be faster (as well as hopefully easier to read and debug)

fixup! Introduced `getNumberDegreesOfFreedom` into conformer class

Better to explicitly check for what you are looking for, than assume that
the exception you catch in a try/catch block is the right one. Makes code
easier to read too.

My question is should we be checking for `Torsion` or is `HinderedRotor` the correct class?

fixup! Introduced `getNumberDegreesOfFreedom` into conformer class

Try/except could catch other exceptions, and suggests that the try ought to work.
Maybe this should actually be a type check on mode (is it an instance of `Vibration`, for example)?

fixup! Introduced `getNumberDegreesOfFreedom` into conformer class

The "else: pass" blocks are redundant.

You may consider chaining all the "if" blocks as "elif", and end with a final
"else:" that raises an "I don't know what this type of mode is!" type of error.

reformat code style, missing colon in `conformer.pyx`

This commit is in response to rwest's suggestions for your pull request
added aromaticity recognition for symmetry calcs

Aromaticity is now perceived in calculating cyclic symmetry numbers.
This commit copies a molecule inside `calculateCyclicSymmetryNumber`,
turns it into an rdkit object, finds all the aromatic bonds and atoms.
The same bonds and atoms in the corresponding rmg molecule object are
then redifined so that the alogorithm is using the correct information.

There is one strange thing about this fix that I dont yet understand.
The unittest thinks cyclic symmetry number of dimethylbenzene is 1
(should be 2). On my local machine, the same
`calculateCyclicSymmetryNumber` function gets it correct, at 2. Also,
i'm inadvertantly printing a bit to stdout, and not sure why it's
happening?

relevant to issues #12, #24, #119, #70, #141

fixup! added aromaticity recognition for symmetry calcs

Better to avoid casting to string if we can - just check if it is None.

fixup! added aromaticity recognition for symmetry calcs

I think this could have been nasty!
atomType is a mutable object. Suppose it was a Cds atom type. What your code would have done,
is change the label on all Cds atom types to be 'Cb'.
   atom1 -> AtomTypeCds -> label -> 'Cds'
would become
   atom1 -> AtomTypeCds -> label -> 'Cb'
instead of
   atom1 -> AtomTypeCb -> label -> 'Cb'

Because the AtomType objects are shared, I think it would have changed them everywhere,
not just in this copy of this molecule.
New (failing?) cyclic symmetry number unit tests.

Not sure if 1,2-DimethylBenzene should have same *cyclic* symmetry number as
1,3-DimethylBenzene? Some more documentation (in the docstrings) about what exactly
this cyclic symmetry number is would help
fixed a couple wip sym tests

there are still some failing tests, but these two were simple fixes.
relevant to 512f25b. I'm still not sure about the total sym no. for
`C(=CC(c1ccccc1)C([CH]CCCCCC)C=Cc1ccccc1)[CH]CCCCCC` nickvandewiele?

assigned sym of wip molecule `C(=CC(c1ccccc1)C([CH]CCCCCC)C=Cc1ccccc1)[CH]CCCCCC`

relevant to 512f25b and 2f9c55e. rmg is computing 9, but I think it's
36... @nickvandewiele?

marked 2 failing sym tests as wip

this was done so travis build doesnt fail
Fix atomType check by checking atomType.label
Return symmetry number = 1 when O-O bond optical isomer found, instead of passing
Fix typo in calculating symmetry by changing bonds to 'Cb', not 'Cd'.
Merge pull request #216 from enochd/master

Introduced `getNumberDegreesOfFreedom` into conformer class and aromaticity for symmetry calculations.
Added cantherm module to read in QChem output files

qchem.py: this new module works reads in information from qchem output
files (e.g., opt+freq jobs, PES scan jobs). In it's present form, it
works, but there is still one more thing that must be added - a read
force constant matrix function. I've been advised to make this commit
earlier rather than later, however. statmech.py is necessarily changed
so that RMG/cantherm recognizes qchem files. In addition, I know I still
have to make unittests, and update the documentation, which I'll get to
shortly. Feel free to test it out and let me know what's wrong.
Updates to qchem module for CanTherm

Mostly bug fixes.
fixup for reading in atomic number in cantherm

didn't realize the qchem mod was not properly reading in atomic numbers.
Caused cantherm to crash when trying to write cartesian coordinates of
species to the output file
Added another example reaction

my isopentoxy example is too big (it has 30+ MB of qchem output files),
so I am adding a smaller one. I will add other small ones in the future
that include pdep. Also, I reverted a change in the C2H4+H example back
to what is on the master RMG-Py brach.
added another example to cantherm

this one is for a unimolecular decomposition reaction using the Qchem
mod
Merge pull request #256 from connie/qchem

Qchem Module for Cantherm.
added atomEnergies for M08SO/MG3S* to statemech

this will be useful in the future when others want to use this method
for thermo calculations.
Correct gaussian environment variable when path is a list

This should not affect the environment variable that provides
a singe path to the g09 executable.

Some systems provide the environment variable as a list of
paths. To correct this, the environment variable
`GAUSS_EXEDIR`, which contains all these paths, is split
at the `:`. Each path is then searched for the g09 executable.
Update RMG example 1,3-hexadiene with multiplicity label
Update RMG example c3h4 with multiplicity label
Update RMG example ch3no2 with multiplicity label
Update RMG example diesel with multiplicity label