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
Making it easier to represent parts of a message as a string
4.1.6 release
Fixing an issue with the history plugin
No longer allowing curl to add a default content-type in the adapter layer
Updating changelog entry
Throwing when you attempt to use "stream" requests in parallel
Test ampersand in multipart field value.
Properly encoding multipart/form-data fields that contain special characters. Closes #758
Only calling curl_multi_select when there are active handles

Calling this function on some versions of PHP can cause the select
to select until the specified timeout value (default of 1 second).
Closes #759.
Improved composer travis install