Update README.md to thank all our wonderful contributors by name!

[coryhouse]

This is long overdue! :) Thanks everyone!

[nickytonline]

@coryhouse I created a CONTRIBUTORS.md file which seems to be more standard. Available via PR #66

[nickytonline]

@coryhouse I spoke too quick. I'm actually not sure what is standard. There is the CONTRIBUTORS.md, package.json file contributors section and also your suggestion to put it in the README.md ¯\_(ツ)_/¯

[coryhouse]

I think you're right that CONTRIBUTORS.md is the most popular standard of the bunch. Thanks for compiling the names!