feat(Request): Also accept query params from POSTed forms

Fixes #170
fix(errors): Remove HTTPUpgradeRequired class

The '426 Upgrade Required' status code is for renegotiating the protocol
used to talk between client and server; the app should rely on the
WSGI server to perform this work.

BREAKING CHANGE: HTTPUpgradeRequired is no longer available, and so
    any apps relying on it will break. This should be a very small
    number of apps, if any, since protocol negotiation should be up
    to the WSGI host, not the app.
feat(falcon.Response): Support wsgi.file_wrapper

This patch adds support for wsgi.file_wrapper, if it is provided by the
WSGI server, to more efficiently pipe resp.stream to the client.

NOTE: Applications do not need to do anything differently; Falcon will
automatically use wsgi.file_wrapper if it is available, and a file-like
object has been assigned to the resp.stream attribute.

See also PEP-0333: http://goo.gl/Y1pbQD

Closes #181
Merge pull request #249 from kgriffs/issues/181

feat(falcon.Response): Support wsgi.file_wrapper
Merge pull request #252 from kgriffs/fix-upgrade-required

fix(errors): Remove HTTPUpgradeRequired class
feat(Request): Also accept query params from POSTed forms

This patch adds support for merging the body of an
'application/x-www-form-urlencoded' request into the params collection
so they can be queried via get_param & Co.

Credit goes to sorenh for the originaly idea and POC. Thanks Soren!

Partially implements issue #180
refactor(request_helpers.Body): Make method definitions explicit

Rather than generating read, readline, and readlines on the fly,
define them explicitly. This is less DRY, but it:

* Makes pylint happy
* Is easier for runtime to optimize/JIT
* Allows us to use proper param names and docstrings
doc: Add FAQ

This patch introduces a new FAQ, and adds some FAQ-like info inline
to doctrings where appropriate. NOTES.md is no longer necessary now
that we have its content properly documented, and so it was removed.
doc(README): Note Python 3.4 support
refactor(util.misc): Remove deprecated functions

Removes percent_escape and percent_unescape, which were deprecated in
0.1.8.
doc: Fixup falcon.util namespaces for misc
chore: Make Travis less chatty on IRC
doc(FAQ): Address authentication question