Replacing github example with httpbin

https://github.com/timeline.json has been removed and delivers a JSON message with a 410 HTTP Status code. The change to http://httpbin.org/get follows the other request examples.
Merge pull request #746 from jeromegamez/fix_timeline_example

Replacing github example with httpbin
Removed whitespace in a test
Cleaning up StreamAdapter and possibly addressing #726
Fixed typo in subscriber example.
Accounting for random connection issues in multi-adapter

This commit updates the MultiAdapter to account for connecitons
being closed unexpectedly and then retried. When this occurs, curl
attempts to rewind the stream before sending. Because we use a
callback function to stream large payloads, curl fails to rewind
the stream and fails the transaction without associating the correct
error code. This commit checks if a transaction has a response
before processing. If a transaction doesn't have a response, then
we attempt to retry the request transparently (without emitting
another set of before events, essentially doing exactly what
curl would have done if it was possible to rewind the stream). If
the request did not have a body, then an error event is emitted as
it is a very weird error. If the request had a body but wasn't
rewindable, then an error event is emitted. If the request had a
body and a rewindable stream, then it is rewound and retried.

This change also updates the MultiAdapter and BatchContext to
transfer until the number of open handles in the BatchContext
reaches 0. This removes some complexity from the main transfer loop
that had to account for pending transactions.

Closes #710
Merge pull request #748 from GrahamCampbell/whitespace

Removed whitespace in a test
Curl cleanup

Ensuring that all curl errors are not retried, just the ones where the
connection could not be rewound.
Ensuring that curl handles are always closed, even if they fail to be
removed from the multi for some reason.
Always calling select in the transfer loop.
Merge pull request #753 from meckhardt/patch-1

Fixed typo in subscriber example.
Allowing mulitple event subscriber listeners to be registered per event name
Merge branch 'no-rewind-fix'
4.1.5 release
Merge branch 'develop'
Merge branch 'master' into develop
Merge tag 'guzzle-v4.1.5' into develop

Conflicts:
	CHANGELOG.md
	docs/events.rst
	docs/quickstart.rst
	src/ClientInterface.php
	src/main/php/puzzle/adapter/StreamAdapter.php
	src/main/php/puzzle/adapter/curl/BatchContext.php
	src/main/php/puzzle/adapter/curl/MultiAdapter.php
	tests/Adapter/Curl/MultiAdapterTest.php
	tests/Event/EmitterTest.php
Incremenal commit - cleaning up merge of guzzle-v4.1.5
Incremental commit - cleaning up merge of guzzle-v4.1.5
Incremental commit - cleaning up merge of guzzle-v4.1.5