v1.4.0

Adds the ability to register a custom log formatter for HTTP logging, and addresses a CORS middleware bug.

CHANGELOG
7e0847f added ability to register custom log formatter (#131)
6257a58 Fix typo in cors.go (#127)
13a38d2 [bugfix] Handle CORS pre-flight request in middleware (#112)
2b8556b Revert "Add Vary header when allowedOrigins is * (#114)" (#122)
9327cfd Add Vary header when allowedOrigins is * (#114)c5874fa distinguish between explicit and implicit star (#118)