Merge pull request #66 from rudimeier/master

Another cmake 3 fix regarding command [ and test.
Added sqlite3 sessions and tests. Fixes to compilerunloop.

Added flag to know when server is listening, to properly stop listening.
Sessions are now a class, with sessions_mem is old mem style sessions, and
new sessions_sqlite3 a sqlite implementation, using json as session data.
Different scenarios may need new session backends.
Added dict read from json, but only onion dict subset.
Merge branch 'master' of github.com:davidmoreno/onion
Added __cplusplus extern "C" guard to sqlite3 sessions.
If can not create sessions (for example permission denied), fail gracefully, just not having sessions.
Properly save sessions at request reuse.
Added precompiled packages section.
Fix #61. Do not show black as pid color on color logging.
Merge branch 'master' of github.com:davidmoreno/onion
travis-ci: add yaml controller