Readme cleanup

I hope this doesn't come off as too pushy, but I noticed some misspellings and odd phrases in readme.md.

I cleaned those up, stripped the trailing white space, and moved the contributing section to CONTRIBUTING.md so the guidelines will be linked on github when someone attempts to create a new PR.

I did also rephrase some of the contribution guide to remove "I" and "me" since talking about the project seemed more communal / welcoming. Again, sorry if that is an over-reach.