Initial import of models
Add models documentstion
Put documentation in astropy's templates
Update docs/models/index.rst
Update docs/models/index.rst
Update docs/models/fitting.rst
Update docs/models/models.rst
Update docs/models/new.rst
Update docs/models/parameters.rst
Update docs/models/parameters.rst
Adding some of the tests from svn converted to pytest
change the default domain range of polynomials
Update astropy/models/__init__.py
use relative imports
Use print function for future compatibility
Move constraints from fitters to models
Add constraints examples
Move scipy imports to functions which use it. Docstrings formatting
Add support for weighted non-inear fitting
Added missing util files and comletely eliminated the use of scipy's comb.