Update mime_type.clj

Add edn to mimetypes
Added ring.util.request/content-type function
Removed references to :content-type request key in core
Mark Ring SPEC as draft
Adjusted formatting on SPEC
Made :request-method SPEC more general (fixes #66)
Removed references to :content-length in core
Moved common HTTP regexes to ring.util.parsing
Added ring.util.request/character-encoding function
Fixed spacing bug in character-encoding function
Removed :character-encoding key from core
Deprecated keys in SPEC (fixes #203)
Merge pull request #118 from greywolve/patch-1

Add edn to mimetypes