Fold TracebackFuture into Future.

Since it is no longer possible for TracebackFuture to modify
concurrent.futures.Future instead, there is no need for separate
classes.  Removing the subclass speeds things up a bit by removing
a level of indirection.

Also microoptimized a few methods of Future.
Microoptimizations for coroutines
* Lazily initialize data structures for YieldPoints
* Get rid of Runner.exc_info
Bring Future support for IOStream read operations into IOStream itself.

This speeds things up in comparison to the _iostream_return_future
decorator by removing unnecessary abstraction and especially by allowing
Futures to bypass some of the hoops IOStream jumps through to ensure a
clean slate for its callbacks.
Remove _iostream_return_future from write and connect as well.
Add a fast path to stack_context when there are no active contexts.

This case is increasingly common now that coroutines are decoupled
from stack contexts.
Add a py26-trollius test case and fix a bug with timedelta on 2.6.
Compress all text/* content types, not just a whitelist.

Closes #982.
Add support for the websocket close status code and reason fields.

Closes #890.
Add python 3.4 tests to tox
Document the fact that tornado.options configures logging by default.

Add tests and comments for how to disable this configuration.
Make it slightly easier to disable by making the command line
flag case-insensitive and allowing `None` instead of the string "none"
when setting the flag in code.

Closes #952.
Catch up on next-release notes.
Fixed automatic port allocation in bind_sockets.

bind_sockets should use the same port on IPv4 and IPv6 if port=None.
Merge pull request #977 from schlamar/fix-port-allocation

Fixed automatic port allocation in bind_sockets.
Disable port-allocation test on mac to avoid annoying firewall prompts.
Add a warning label to WSGIContainer.
Fix bit-rotted app engine tests.

sys.argv is no longer empty in dev_appserver.
define and use errno_from_exception abstraction

If an OSError or IOError are instantiated without an errno value, e.g.
e = OSError(). The existing code would give an IndexError: tuple index
out of range. However there have been cases that the errno attribute
wasn't populated so instead of switching to it this introduces a helper
function to ensure we get the errno value through whatever means
possible.
update Template Loader with 'with' statment
Merge pull request #999 from mengzhuo/master

update Template Loader with 'with' statement
Exclude another timing-sensitive test from the travis build.