[Android] update of speechrecognizer plugin for phonegap 1.7

I've updated the speechrecognizer plugin to work with the changes caused by the switch from phonegap to cordova.
Tested with phonegap 1.7

Also updated the readme because it had references to speechrecognizer.js whereas the filed is named "SpeechRecogniser.js" (different case) which caused the plugin not to be found in the android app.