Large Payload support for iOS 8

Fixes #181
Fixed node 0.10 behaviour
Corrected engine requirement

EPIPE Fix requires changes made in 0.6.14. In reality it probably makes sense to drop support for anything before 0.8 or 0.10 but I haven't seen a need to do so yet.
Connection retry limit
Documented the connectionRetryLimit
Merge branch 'feature/ssl-failure-abort' into develop
Restructured documentation.
Remove a socket from the pool when a timeout occurs

In some cases timeouts are occurring but the socket isn't fully closing. Because of this the maximum number of open sockets is reached and no further notifications are sent. (Issue #156)

When a timeout occurs the socket is now removed from the pool to ensure new sockets can be created.
v1.6.0
Merge branch 'develop'