add travis scripts
add libgmp-dev to required packages
add ctypes dependency
CCM ciphersuites
remove unused open
provide auth_header function (which returns the authentication header), called by mac
remove mac from crypto_context
define records for the various cipher_states, also introduce CCM
use the records of the ciphers in engine, and also support CCM
distinguish privacy protection in ciphersuites by being
Stream, Block or AEAD, as specified in RFC5246.
adapt to changes (esp key_length), and emit a cipher_state directly

rework keyblock slightly to meet the current demands:
 CCM in TLS_1_2 requires 4 bytes as 'implicit_nonce' from the keyblock (as IV, where block ciphers in TLS_1_2 do not need any IV) [could have used mac for that, since AEAD do not use hmac, but that would be in violation with rfc5246]
adapt get_cipher to recent changes, provide ccm_encrypt/ccm_decrypt
advertise CCM ciphersuites
update CHANGES