Removed unused enacl lib. Use eblake2 for hash. (aeternity#8)

* Removed unused lib.

* Replace local blake2 implementation with eblake2.

* Add eblake2 dep to app file.

* Add eblake2 to rebar config.

* Use hex for eblake2.

* Bump version.

* Replace local rlp with aeserialization repo. Use ref till first release is available.

* Remove unused vars.

Add annotations (comments) to bytecode. Add strip function to remove …

…symboltable and annotations from bytecode.

Initial CircleCI integration (aeternity#5)