add isConnected method

I converted my application from AutobahnAndroid to android-websockets
to take advantage of ssl support.
android-websockets did not have a isConnected method, which is used in
my application, so I implemented one.
Merge pull request #13 from pefoley2/master

add isConnected method and remove incorrect annotations.
Update SocketIOClient.java
Fix syntax errors in README.md's example code
Merge pull request #15 from cpeterso/cpeterso/fix-readme-errors

Fix syntax errors in README.md's example code
Added support for Endpoints
Added listener event for connecting to endpoints
Merge pull request #16 from vinaysshenoy/master

Added Support for Endpoints
Merge pull request #14 from orenda/patch-1

Update SocketIOClient.java - onError failed on nullPointerException
Added support for Acknowledges
Update README.md
add end pointed connected override to the handler

the new endpoint connected callback is mandatory in the handler
interface, without it the README example doesn't work
only socketio client has endpoints, normal websocket doesn't
Merge pull request #18 from liorsion/master

README fix for endpoint callback
Update README.md

The update for onConnectToEndpoint() got overwritten by my changes for Acknowledges. Adding the method back to the README.
Added support for Acknowledges
Merge branch 'master' of
https://github.com/vinaysshenoy/android-websockets.git
Avoid mSocket NPE if WebSocketClient.disconnect() is called twice
Merge pull request #19 from cpeterso/cpeterso/handle-double-disconnect

Avoid mSocket NPE if WebSocketClient.disconnect() is called twice
Fixed merge conflicts