feat($cordovaBatteryStatus): bringing the events in a angular way

- adding tests
- $on implementation

BREAKING CHANGE: bringing the events in a angular way

To migrate the code follow the example below:

Before:

$cordovaBatteryStatus.onBatteryStatus(function(result) {
  var batteryLevel = result.level;       // (0 - 100)
  var isPluggedIn  = result.isPlugged;   // bool
});

After:

$cordovaBatteryStatus.$on('batterystatus', function (result) {
  var batteryLevel = result.level;       // (0 - 100)
  var isPluggedIn  = result.isPlugged;   // bool
});
Fix readFileAbsolute

Accept parameter and return promise
Merge remote-tracking branch 'upstream/master' into feat-battery-status-angular-events
test($cordovaBatteryStatus): add more tests
Issue #325: Adding option on writeFile to append data on EOF, instead of always erasing existing file, if any
Merge pull request #326 from Natsu-/plugin_file_write_append_option

Issue #325: Adding option on writeFile to append data on EOF
Merge pull request #260 from alexluke/readFileAbsolute

Fix readFileAbsolute
Merge pull request #297 from mrzmyr/feat-battery-status-angular-events

feat($cordovaBatteryStatus): bringing the events in a angular way
fix($cordovaStatusbar): honor overlaysWebView boolean argument

- fix the method overlaysWebView to honour the boolean param
- add unit test for it

fixes #167, #168
Merge pull request #329 from mrzmyr/test-status-bar-boolean-check

fix($cordovaStatusbar): honor overlaysWebView boolean argument
chore(dist): rebuild
chore(plugins): replace window with angular $window