Refactor code around initialization and error strings.

@vhbit I implemented my interpretation of the conversation on #65. I'm not familiar with any other locations that we should invoke: `ffi::init()`. I moved the statics that init relies on into `ffi.rs` as well, let me know if something else is preferred. I got two successful builds back on my fork, hopefully there are no more build issues. 
This doesn't seem like quite the right place for this. Why not leave it in the ssl module?