SJCL from Bower and a custom build

* Fixes #7 
* SJCL now pulled from Bower 
  * built using `./configure --without-random --without-ocb2 --without-gcm --without-ccm`
  * wrapped into an AMD module

Library Size:
```
build/fxa-client.js (with comments)
Size:		52.89 Kb
Gzip Size:	15.52 Kb

build/fxa-client.min.js
Size:		22.07 Kb
Gzip Size:	8.41 Kb
```