Handle media types with parameters

Some media types included in the "Accept" header include parameters. These
media type parameters are distinct from "q" and any other "accept-param", and
are listed before "q". With this patch these parameters don't cause errors.
(See sections 3.7 and 14.1 of RFC2616 for more information.)
Handle media types with parameters

Some media types included in the "Accept" header include parameters. These
media type parameters are distinct from "q" and any other "accept-param", and
are listed before "q". With this patch these parameters don't cause errors.
(See sections 3.7 and 14.1 of RFC2616 for more information.)
Merge branch 'mediatypeparameters' of github.com:jessaustin/werkzeug into mediatypeparameters

Conflicts:
	werkzeug/http.py
merge with changed test
Link Python 3's syntax bug
Link to older ticket

This is embarrassing.
verbose _accept_re, as requested
Add changelog
Merge branch 'mediatypeparameters'

Fix #205
Fixes Accept.best_matches

Only includes Accept items in consideration for best_matches if they have q>0, as a quality of 0 should be equivalent to not being included in the list at all. 

This agrees with RFC2616 (http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.9): 
```
If a parameter has a quality value of 0, then content with this parameter is `not acceptable' for the client.
```
Adds test cases for Accept, including best_match

One test is an expected failure. This is because the
current implementation does not correctly implement
specificity. I tried decorating this with
@unittest.expectedFailure, but that didn't work for
python 2.6 so I've now commented out that test instead.

The problem is if the accept header on the request is:
`Accept: x;q=0,y;q=0.5,*;q=1`
Then `x` should never be the best match because it has
been specifically declared as q=0. However, in the current
implementation, werkzeug will see *;q=1 first and decide
that everything matches the wildcard. This is not correct
behaviour according to RFC2616, as an `x` should match the
specific entry for `x` rather than the wildcard entry `*`,
but more substantial changes would be needed to fix this.
Merge branch 'fix/accept-best-matches-quality-zero'

Fix #536
Add changelog entry for #536