Support for parameters in mime types.

[JonMidhir]

Fixes #1141.

Adds support for parameters when creating new mime types.

Previously, the user could declare a mime type with parameters like this:

configure do
  mime_type :rss10, 'application/rss+xml; version="http://purl.org/rss/1.0/"'
end

get '/feed', :provides => [:rss10] do
  # ...
end

But the route would 404 when the version was missing from the accept header:

curl -H 'Accept: application/rss+xml' -I [host]/feed

HTTP/1.1 404 Not Found 
Content-Type: text/html;charset=utf-8

This change allows the route to respond, including the more specific parameters in the Content-Type header.

curl -H 'Accept: application/rss+xml' -I [host]/feed

HTTP/1.1 200 OK 
Content-Type: application/rss+xml; version="http://purl.org/rss/1.0/"

Accept headers that include all, some or none of the specified parameters are OK, but those that specify different values are not.

configure do
  mime_type :rss10, 'application/rss+xml; version="http://purl.org/rss/1.0/"; charset=utf-8'
end

# OK
curl -H 'Accept: application/rss+xml' -I [host]/feed
curl -H 'Accept: application/rss+xml; version="http://purl.org/rss/1.0/"' -I [host]/feed
curl -H 'Accept: application/rss+xml; version="http://purl.org/rss/1.0/"; charset=utf-8' -I [host]/feed
curl -H 'Accept: application/rss+xml; charset=utf-8; something=else' -I [host]/feed

# Not OK
curl -H 'Accept: application/rss+xml; version="https://cyber.harvard.edu/rss/rss.html"' -I [host]/feed

[zzak]

Thank you @JonMidhir!

I'd like to consider this for after a 2.0 release.

[JonMidhir]

Noticed a few stray commits in this, rebased them so it's much simpler now. Also, master had moved on a fair bit 😂

[namusyaka]

Marked as v2.1.0.