ENH: Function dictionary created in physics_model

- Working on imports from lmfit
ENH: Valid fitting model lists

- Added a list to physics_peak and physics_model that contain
  the lists of valid options
MNT: Py3 bug fixed?
BUG: fixed the radius_to_twotheta for the mistake.
changed it to np.arctan(radius / dist_sample) from 2*np.arctan(radius / dist_sample)
Removed lineshapes_dict and turned it into a sorted list
MNT: PEP8
BUG: Fixed py3 bug
Merge pull request #192 from sameera2004/e_radius_to_2theta

BUG: fixed the radius_to_twotheta code for the mistake.
MNT: Changes by @tacaswell
ENH: Subclassed lmfit models to rewrite the docs

- This is so that we don't lose the parameter guessing that is
  built in to lmfit but we do get the docstrings we need
MNT: Fixed merge conflicts
MNT: Removed print statement
MNT: Refactored VisTrails specifics to VTTools
MNT: Moved test_fitting to VTTools
MNT: Renamed project to scikit-xray
Merge pull request #193 from ericdill/repo_rename

MNT: Renamed project to scikit-xray
Update README.md
MNT: Local merge due to rename conflicts
MNT: Major refactor of fitting

- Updated fitting code to more closely mirror lmfit's codebase
Merge remote-tracking branch 'dill/fit_dict' into fit_dict