We only depend on cryptojs for this webcrypto polyfill, so let Grunt
concatenate them into one file.
The reference in the getString helper isn't needed since we use the
built in string converters on CryptoJS's word arrays.
Rename methods on the curve25519 interface to be a bit more high level.
Cleanup emscripten wrapper class, wrap long lines and such. Also add a
grunt task alias for building the emscripten compiled curve
implementation.
Build with `grunt compile && grunt concat:curve25519` after installing
emscripten.
Enable by either (a) not loading nativeclient.js or (b) setting
`textsecure.NATIVE_CLIENT = false` before loading nativeclient.js.
