Merge pull request #397 from hintjens/master

Removed zservice class
add zcert_save_secret
Merge pull request #400 from genjix/master

add zcert_save_secret
added zcert_save_secret() to documentation.
Merge pull request #399 from hintjens/master

Fixed #398
Removed selftest of deprecated wrap/unwrap
Fixed memory overread in chunk_load
Minor cleanups
Removed custom frame API

- deprecated by zproto, which is better for real protocols