Added the new input variables from the XML input file to the SFRdata class.

Also incorporated most of build_SFR_package function. NEED TO STILL HANDLE SEGMENTS2MODIFY!!
Merge pull request #33 from hwreeves-USGS/hwrclassy

Hwrclassy
Added in the ElevsFromContours class from Andy.
Merge remote-tracking branch 'upstream/classy' into classy
Merge pull request #34 from mnfienen/classy

Classy
Merge remote-tracking branch 'upstream/classy' into hwrclassy