Converted tests to Jasmine test framework

Added the Jasmine test framework (no other dependencies were added).  

Converted all existing tests to Jasmine. 
Note: some messages reported the block as the key and vice-versa, fixed in the new tests.  

Added some test cases for openpgp.write_encrypted_message(..), .write_signed_and_encrypted_message(..), and .generate_key_pair(..).