add instance method adsorp_atom() of Slab and its unittest
add instance method adsorp_atom() of Slab
change xyz=0 to coords_are_cartesian=False, fix distance calculation.
Vastly simplify add absorbate code.
Merge branch 'surface' of github.com:materialsproject/pymatgen into surface
Merge branch 'master' into surface
Update surface.py

Updated version of surface.py. The method in the Slab class has been modified to allow for the enumerating of different termination sites in a slab. A unittest has been added to see if the .cif files generated to represent the slabs with different termination sites has been properly generated
Merge pull request #115 from richardtran415/surface

Update surface.py
Update surface.py
Update surface.py

Boolean to standardize cells set on True by default. Its possible there still might be some issues with unit test. I will try to push the required cif test files needed to operate the unit test correctly
Merge branch 'richardtran415-surface_terminations' into surface
Merge branch 'surface' of https://github.com/richardtran415/pymatgen into surface

Conflicts:
	pymatgen/core/surface.py
Update surface.py
changes made to surface.py script
Merge branch 'surface' of https://github.com/richardtran415/pymatgen into surface

Conflicts:
	pymatgen/core/surface.py
Merge remote-tracking branch 'upstream/master' into surface
Merge branch 'surface' of https://github.com/materialsproject/pymatgen into surface
Update surface.py
updates to surface.py
Merge branch 'surface' of https://github.com/materialsproject/pymatgen into surface

Conflicts:
	pymatgen/core/surface.py