example: fix typo in doc http to https

ssl_hello_world_example uses https instead of http.
Fix echo_get/README.md
Fix the SPDY suite for R15
Merge branch 'patch-1' of git://github.com/edgurgel/cowboy
Fix a small typo in a test
Nicer error when NPN isn't available
Merge branch 'typofix' of git://github.com/Etsukata/cowboy
Clarify functions that can only be called once