Intial version of CCM and FM reddening functions.
Move reddening to specutils/utils.
Cleaned up, and made many minor modifications based on comments
from kbarbary. Also changed to return reddening curve rather
than dereddened flux.
GCC09 and FM07 models are currently not properly functioning due
to problems with those two papers. Framework left in, but models
are not allowed to be used for now.
Renamed to reddening_ccm and _fm. Corrected line continuation
of an error string.
Merge pull request #12 from dsyphers/reddening

Dereddening functions - might need some rewording in the docstrings. Needs documentation how to use.