Tweak event handler a bit for clarity

Put cases in the order we expect them to occur

Swallow responses to internal pings

Mongoose example for server data push

Fix VS2013 warnings

Fix ssl close with polarssl

Possible fix in order not to loose the reference of connection_param pointer

Implementing array varibles

Adding mg_vprintf and mg_vprintf_data.

Fix default windows FD_SETSIZE, closes #506

https://support.microsoft.com/en-us/kb/111855 describes
that the user is expected to set the FD_SETSIZE macro
before including winsock2.h

Fix mjpg_streamer example

Inspect POST buffer in mg_get_var() only if first call of get_var() returns -1

Add a Gitter chat badge to README.md

In mg_get_var() the first call of get_var() inspects the variables of
the query string. If the requested variable is found but the destination
buffer is too small to hold the variable, return -2 right away. If it's
not found, make the second call of get_var() to inspect the POST buffer.

Reverting (socket < 0) checks to avoid Windows build failure.