Adding a first version of PushoverHandler

The PushoverHandler sends messages to api.pushover.net. The class depends on the SocketHandler
I modified the SocketHandler to make it possible to change the port for subclasses (Pushover needs the explicit port 80 to work)
The tests only see if the content sent to the api is correct. The rest should be already covered in the tests for the Sockets.
Rewriting the write method

Before, the write method would alter the $record array and then call parent::write().
Now the method builds the string which should be written into the stream and then does it himself.
I had to change two methods to be protected so the PushoverHandler could call them.
Changing the SocketHandler to call generateDataStream when writing to socket

Now the write method does not to be overwritten when the format of the dataStream the Socket sends has to be altered in any way the formatter cannot handle (See the PushoverHandler for an example)
Overwriting the generateDataStream method to format the Data sent to Pushover

This way, the write method does not have to be overwritten.
Changing typo in variable name and default title for pushover message
Change visibility back to private
Merge remote-tracking branch 'Sgoettschkes/PushoverHandler'
Update README
Specify port in the connection string instead of adding a protected property
Change the default pushover title to the hostname
CS fixes