update readme

Author: dominictarr

readme.markdown

@@ -1,20 +1,45 @@
 # crypto-browserify
 
-A (partial) port of `crypto` to the browser.
-
+A (partial) port of node's `crypto` module to the browser.
 
 [![travis](https://secure.travis-ci.org/dominictarr/crypto-browserify.png?branch=master)](https://travis-ci.org/dominictarr/crypto-browserify)
 
 [![browser support](http://ci.testling.com/dominictarr/crypto-browserify.png)](http://ci.testling.com/dominictarr/crypto-browserify)
 
+The goal of this module is to reimplement node's crypto module,
+in pure javascript so that it can run in the browser.
+
+Here is the subset that is currently implemented:
+
+* createHash (sha1, sha256, md5)
+* createHmac (sha1, sha256, md5)
+* randomBytes
+
+## TODO
+
+The highest priority unimplemented features are
+
+* createDiffieHelman
+* createCipher (aes)
+* createDecipher (aes)
+* createSign (rsa)
+* createVerify (rsa)
+
+## contributions
+
+If you are interested in writing a feature, please create implement as a new module,
+which will be incorperated into crypto-browserify as a dependency.
+
+All deps must be compatible with node's crypto
+(generate example inputs and outputs with node,
+and save base64 strings inside JSON, so that tests can run in the browser.
+see [sha.js](https://github.com/dominictarr/sha.js)
 
-Basically, I found some crypto implemented in JS lieing on the internet somewhere
-and wrapped it in the part of the `crypto` api that I am currently using.
+Crypto is _extra serious_ so please do not hesitate to review the code,
+and post comments if you do.
 
-In a way that will be compatible with [browserify](https://github.com/substack/node-browserify/).
+## License
 
-I will extend this if I need more features, or if anyone else wants to extend this,
-I will add you as a maintainer.
+MIT
 
-Provided that you agree that it should replicate the [node.js/crypto](http://nodejs.org/api/crypto.html) api exactly, of course.