improve ocamldoc of Cohttp.S
bump to 0.15.0
Merge pull request #221 from avsm/master

improve ocamldoc of Cohttp.S
add base64 module to .merlin
Base64 -> B64 rename
constrain base64 to 2.0.0 and above
Merge pull request #222 from rgrinberg/base64_fix

Base64 fix