add Encrypt/Decrypt function to pull-crypto

Let me know what you think. I added a bunch of tests and also updated the readme. Please let me know what happens after running the `allCiphers.js` test. I am running OSX 10.7.5 and I am failing on about 12 ciphers. I had to blacklist the `aes-xxx-xts` ciphers because they were giving me max call stack errors. I am not even sure if this test should be included since it seems unpredictable. The way I wrote it, its passing 109 tests but it may fail on your system, I am not sure. I checked out the link you sent for the node core tests for `crypto`. It looks like they don't go very deep at all for checking different ciphers. I only caught a few references to different algorithms. Looks like they really only test 4. `des-ede3-cbc` and a few AES (`aes-256-cbc`, `aes256`, `aes192`).

Please note I did all the work for this fork on the cryptostream branch just so any changes resulting from this request can be done without having to worry about affecting master.

I also slightly modified the readme on your `hashes` example to include `pull.values` since when I copied and pasted that code I got error that `values` is `undefined`.