Previous implementation was not OFB at all, and fail tests.

Note: This implementation is for fixed width 128-bit IV which makes
shift regiser redundant.

Full test of OFB to match GOST R 34.13-2015 test vectors is impossible,
due to test IVs are having size (256-bits) over the maximum openssl can
allow (128-bits).

I generated new test vectors from canonical implementation
from `PR_GOSTR_bch_v9.zip` (revision of 2016-10-28) by truncating test
IVs in half.

Make sure stream modes can encrypt any block size.

Previously CTR did not continue unfinished block on the next cipher
iteration.

test_grasshopper: test modes to match GOST vectors
Only ECB and CTR modes are tested. OBF, CBC, CFB modes is not testable
under openssl.

Offset commit 7f572e958b13041056f377a62d3219633cfb1e8a
Old openssl still needs EVP_MD_FLAG_PKEY_METHOD_SIGNATURE flag to be
set.

Fix a mem leak

Ensure the grasshopper ciphers are destroyed on engine destroy.

modernize ci

(*) convert 'openssl ciphers | grep ...' into Test:More syntax
(*) enable some tests on travis-ci (04 is yet broken)

modernize ci

initial travis-ci support

Redundant values removed