Fix Beep exception on Android when no argument passed

In iOS, if you call the beep function and don't provide a count, it
plays a single beep. On Android, however, it always attempts to load the
fix object in the array, which is null if no count is provided, causes
an exception to be thrown, and no beep to occur. The simplest fix for
this is to simply pass `1` if no count is provide from the web.

close #20
android: Explicitly apply default theme to dialogs

When you don't specify a theme the platform defaults back to gingerbread
styling. By applying the device default theme it will change it to the
new (and much nicer looking) styles on newer devices.

close #18
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/cordova-plugin-dialogs