unfiltered-filter depending on servlet-api 3.0.1

[Nathan Hamblen]

In order to read the status code from a response object, we're going to
be updating to servlet-api version 3.0.1 (released 2011). Does anybody
have any concerns about this change, or feel that it should be in a new
major version? It's currently merged into the 0.8.2 branch.

https://github.com/unfiltered/unfiltered/pull/259/files#diff-94e9cbae23937333d680df485895deebR6