Add CONTRIBUTORS.md file. Closes #36

Add note to README.md about Python 3 support. Closes #37

CONTRIBUTORS.md

@@ -0,0 +1,12 @@
+# Contributors
+
+## Special thanks to all the people who helped improve this project with code, documentation and bug reports so far:
+
+* [ConorIA](https://github.com/conoria)
+* [00dani](https://github.com/00dani)
+* [ekevoo](https://github.com/ekevoo)
+* [snowmanninja](https://github.com/snowmanninja)
+* [sparky005](https://github.com/sparky005)
+* [varjmes](https://github.com/varjmes)
+* [meggle](https://github.com/meggle)
+* [superstrong](https://github.com/superstrong)

README.md

@@ -1,6 +1,8 @@
 # Heroku_ebooks
 
-This is a basic Python port of [@harrisj's](https://twitter.com/harrisj) [iron_ebooks](https://github.com/harrisj/iron_ebooks/) Ruby script. Using Heroku's scheduler, you can post to an _ebooks Twitter account based on the corpus of an existing Twitter at pseudorandom intervals. Currently, it is the magic behind [@adriennelaf_ebx](http://www.twitter.com/adriennelaf_ebx) and [@stevebuttry_ebx](http://www.twitter.com/stevebuttry_ebx).
+This is a basic Python port of [@harrisj's](https://twitter.com/harrisj) [iron_ebooks](https://github.com/harrisj/iron_ebooks/) Ruby script. Using Heroku's scheduler, you can post to an _ebooks Twitter account based on the corpus of an existing Twitter at pseudorandom intervals. Currently, it is the magic behind [@adriennelaf_ebx](http://www.twitter.com/adriennelaf_ebx) and [@stevebuttry_ebx](http://www.twitter.com/stevebuttry_ebx), among many, many others in the wild.
+
+This project should work in the latest releases of Python 2.7 and Python 3. By default, in Heroku, this will be deployed to Python 3.
 
 ## Setup
 
@@ -56,5 +58,6 @@ If you want to avoid hitting the Twitter API and instead want to use a static te
 
 
 ## Credit
-As I said, this is based almost entirely on [@harrisj's](https://twitter.com/harrisj) [iron_ebooks](https://github.com/harrisj/iron_ebooks/). He created it in Ruby, and I wanted to port it to Python. All the credit goes to him.
-As a result, all of the blame for clunky implementation in Python fall on me. If you see ways to improve the code, please fork it and send a pull request, or file an issue for me and I'll address it.
+As I said, this is based almost entirely on [@harrisj's](https://twitter.com/harrisj) [iron_ebooks](https://github.com/harrisj/iron_ebooks/). He created it in Ruby, and I wanted to port it to Python. All the credit goes to him. As a result, all of the blame for clunky implementation in Python fall on me.
+
+Many thanks to the [many folks who have contributed](CONTRIBUTORS.md) to the development of this project since it was open sourced in 2013. If you see ways to improve the code, please fork it and send a [pull request](https://github.com/tommeagher/heroku_ebooks/pulls), or [file an issue](https://github.com/tommeagher/heroku_ebooks/issues) for me, and I'll address it.