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.
correctly handle empty POST parameters
Accumulated release note updates.
Flushing the buffer when calling IOStream.read_until_close()

Ran into this when calling IOStream.read_until_close() after calling
IOStream.read_until("\r\n"), leaving data in the buffer.
Added test_streaming_callback_with_data_in_buffer to iostream_test.py
Python3 compatibility for test_streaming_callback_with_data_in_buffer
Add @gen.coroutine and gen.Return for future-based (and py33-style) coroutines.
Convert auth methods from return_future plus gen.engine to gen.coroutine.
Test twisted and cares resolvers in netutil_test.
Convert resolvers to @gen.coroutine.

This adds a requirement that there be a "current" IOLoop, which introduced
a few ripples.
Fix resolver test script.
Merge pull request #686 from omribahumi/master

Flushing the buffer when calling IOStream.read_until_close()
Fix twisted version check.