feat(social-sharing): add canShareViaEmail (#333)
feat(social-sharing): add canShareViaEmail (#333)

* - Add support for canShareViaEmail
- Make the following parameters in shareViaEmail method optional: cc, bcc, files
- Add usage for canShareViaEmail and shareViaEmail
- Fix some formatting to be more consistent
- Fix pluginRef

* Fix import

xueron/ionic-native,driftyco/ionic-native,xueron/ionic-native,klirix/ionic-native,xueron/ionic-native,ramonornela/ionic-native,klirix/ionic-native,ramonornela/ionic-native,xueron/ionic-native,klirix/ionic-native,ramonornela/ionic-native,driftyco/ionic-native,driftyco/ionic-native,ramonornela/ionic-native