add a props dict as an attribute to Species

this allows the user to store user-defined, and arbitrary
key-value pairs of his/her choice.

Conflicts:[RESOLVED]

	rmgpy/species.py
add props attribute in constructor as parameter and default to empty dict

this is more flexible than setting it in the constructor to an empty dict.
This way, one can also transfer a properties dict from elsewhere.

Conflicts:[resolved]

	rmgpy/species.py
add props parameter when calling constructor of species.Species

Conflicts:[RESOLVED]

	rmgpy/rmg/model.py
add cythonized props dict in species.pxd
add documentation in rmgpy/species.Species on props attribute
added test in speciesTest for props dictionary attribute of Species.

testing if props attribute is a dictionary, and if dictionary entries
are properly stored.
Merge pull request #278 from nickvandewiele/props_species_refactor

Add props dictionary attribute to the Species class for storing various user-defined properties.
test checking multiplicity parsing of group
Correct the new testFromAdjacencyList_multiplicity unit test.

Written by a java dev :-)
Fix bug in parsing group adjacency list multiplicities.

Also added comments for the somewhat complicated reg-ex.
Thanks for finding the bug, Nick.
Added another unit test for parsing multiplicity lists in group adjacency lists.
Merge pull request #281 from rwest/multiplicity-regex-bug

Multiplicity regex bug
model comparison
Cleaning up all the unnecessary files!
Pruning documentation is added!
Merge pull request #288 from KEHANG/official-doc

Pruning documetation added
correct initialization of props attribute to object attribute

by defaulting to None rather than {}, the props attribute becomes a
object attribute rather than a (shared) class attribute.
unit test showing the behavior of props dicts in Species

the props attribute should always be a local object attribute,
never shared among other instances.
Rename a couple of unit tests

The first line of the test docstring ends up in the unit test nose log,
so it's good to be succinct.
Merge branch 'pr/293' to fix Species.props dictionary.

Closes #292 and #293