Implement additional error handling in utils.import_object function
Merge remote-tracking branch 'upstream/master' into import-object
import_object will raise standard ImportError even in case of Value/Attribute error
Adding support to override, via static_url, whether the generated URLs
should include the version signature or not.
Introduce StaticFileHandler.(get_content|set_headers) which reduces the
complexity of the HTTP GET handler of static resources.
Fixed syntax error in the altered StaticFileHandler.get() method
Move retrieval of absolute path to separate method which is also in
charge of validation.
Cache the computed absolute path to the requested resource in
StaticFileHandler. The cache is cleared on_finish of each request
in order to ensure recomputation on each request.
Restore context for all read methods.

Prior to 2db0aceb32f5c042f5306e72a4679580b4359f34 this was being done
properly, but the refactor removed stack_context.wrap causing some issues
in our upstream context managers.
Merge pull request #521 from yoinc/master

Restore context for all read methods
Final 2.3 release notes
Set version number to 2.3
Timeouts in SimpleAsyncHTTPClient now raise HTTPError

Previously, they ran the callbacks themselves.
Post-release version bump
Set alarms on child processes in process_test.

These alarms used to be there, but got dropped in a previous change
because I had assumed the child processes would inherit the parent's
alarm.
Update README to match tornadoweb.org
Use https for all links to github.

Github redirects everything to https anyway, so the links might as well
start out secure.
Factor out gzip decompressor from SimpleAsyncHTTPClient into util.GzipDecompressor
Factored out body argument-parsing code into httputil.parse_body_arguments

Parses application/x-www-form-urlencoded or multipart/form data)

Was duplicated in httpserver and wsgi
Add testing.AsyncSSLTestCase

Allow subclasses of AsyncHTTPTestCase to provide their own http client
and server implementations.