Create a contrib project for mage

[wfscheper]

There are always desired features or functionality that either need time to fully bake before inclusion or don't really belong in the core of a project like mage. One way other OSS projects manage contributions of this sort is to create a contrib project.

This purpose of this issue is to start a conversation about creating such a space for contributions to mage. Some items that will need decisions are:

• what are the rules for inclusion in contrib
• what are the rules for contrib code moving into mage itself
• how are releases of contrib projects managed (go submodules?)
• how are contributions included? (git submodules? Direct pull requests?)

I'm sure there are other decisions as well.

[natefinch]

Yeah, this is a good idea