Add ability to specific different develop branch

[mathomp4]

Right now mepo develop will only use what's in the components.yaml. But, we should be able to have, say mepo init --develop=dev/gocart and have mepo know internally that develop is now dev/gocart say, and not develop.

Also, have different ways to specify this:

1. mepo init --develop
2. With an rc file
   1. Look for $MEPORC in environment
   2. Default to using ~/.meporc

Next question is how to do this and "override" the develop: in the components.yaml

[tclune]

Probably need to develop slightly different terminology here. We probably still need the notion of "true" develop when those team branches go to the next step to merge. I think calling them a team branch or a community branch would suffice.