Initial libev support

Several issues still remain:

* connections are not freed until the server shutdown
* several additional memory leaks
* introduced an additional dependency in listener.c upon connection.c
* error handling in callbacks needs some review
Update .travis.yml
Use size_t for length on parse functions.

Conflicts:
	src/listener.h
merge in master
Merge branch 'master' (early part) into libev
Merge in master
Free connections on close
Merge branch 'master' into libev
Merge branch 'master' into libev
Remove unused TAILQ_FOREACH_SAFE macro
Merge branch 'master' into libev
Reorder functions in connection.c
Cleanup connection.c

Fix lines over 80 characters
Make connection.listener const
Merge branch 'master' into libev
Record client address on accept
Link to libev
Fix connection leak
Merge branch 'master' into libev
Merge branch 'master' into libev
Move state logic