Jnf/mission statements

- Adding a folder for mission statements.
- Adding a collection of markdown files w/ descriptions of what purpose each mission statement format serves.
- Adding a simple gitignore to make working on OS X tolerable.
- Adding a couple notes to the `README` about essays I'd like to discuss/write/read.
- Adding tweet-sized and bio-sized mission statement drafts.

With regards to the drafts, I propose we work in a branch (this one or another, I don't care), submitting/reading/editing words until we're both happy with them. I don't think we need issues with this. I'm perfectly happy to use a PR to comment/refine. Thoughts?