Added folder monitoring capability and fixed emulator launching problem.

- The folder monitoring allows users to add one or more native android
apps on fly and selendroid immediately signs and adds these files to
the app store so they can be used without restarting the node.
- Adding one seconds wait before calling "isDeviceReady" to avoid the
command sent too quickly while the emulator still starting and not ready
to receive any commands

Signed-off-by: Binh Vu <bvu@paypal.com>
Typo here. should probably say -- "The folder which contains Android applications under test" 

Furthermore, you probably want to make mention that the folder will be monitored for new applications during the lifetime of the selendroid node. To this point, perhaps we want to add another config option (something like -disableFolderMonitoring) which only loads the apps from -folder at startup and never monitors. Of course, one could argue that is equivalent to simply using the pre-existing -aut option. So maybe the additional config option  is not necessary.