basic, experimental support for fbc
Merge pull request #3 from opencobra/master

Back merging reaction patch from opencobra:master
Merge pull request #4 from opencobra/master

Pulling in patches from opencobra:master
Bringing in the patches from the master branch
Merge branch 'master' into sbml_fbc
added in a test for fbc package
updated the fbc test to only run if the package is present.
Updated sbml write test to default to SBML+cobra if fbc package is unavailable
Updated sbml write test to default to SBML+cobra
Merge branch 'sbml_fbc' of github.com:danielhyduke/cobrapy into libsbml_fbc_travis