Vacancy class considers species and no. of struct

Vacancy.make_supercell_with_defects method is updated with options to
specify the site species and the number of super cells to be returned
Merge branch 'master' of https://github.com/mbkumar/pymatgen
Bug fix
Merge branch 'master' of https://github.com/mbkumar/pymatgen
dilute_solution_model.py added to analysis.defects

DiluteSolutionModel used to compute defect concentrations
is added
Merge branch 'master' of https://github.com/mbkumar/pymatgen
fix QChem vibrational frequency parsing
Merge remote-tracking branch 'origin/master'
Minor changes to maker; Speed up analyzer.
Add functionality to return a ComputedStructureEntry from a Vasprun.
Significantly improve functinoality of Vasprun.get_computed_entry. Also
streamlined hive code for new Vasprun./
Merge remote-tracking branch 'mpmaster/master'
Use monty.serialization for YAML and JSON loading. Requires monty>=0.2.4.
Switch to yaml for VTK color schemes.
Use refactored monty serialization.
More refactoring.
More YAML refactoring.
Modular dilute_solution_model and unit tests

The function dilute_solution_model is modularized
and accepts trial chemical potentials as input and can generate either
the defect concentration plot or  defect formation energies only.
In addition unit tests are added for dilute_solution_model
Comment removal
Merge branch 'master' of https://github.com/mbkumar/pymatgen