EmailComposer plugin version 2.0

- support for Cordova plugman (adding plugins via the cordova cli)

- support for `cordova.require()` loading of the plugin

- migrated to  Cordova 2.x plugin specification (a la `CDVInvokedUrlCommand`)

- support for one or more file attachments in the e-mail message;
  attachments can be a file on disk, a UTF-8 string (i.e., text/html),
  or base64 encoded data (i.e., image files generated in memory)

- JavaScript backwards compatability support for both v1.0 of this plugin
  and the EmailComposerWithAttachments plugin

- support for XCode unit tests via a manually mocked MFMailComposeViewController