Ensured that all platform channel use is protected on iOS.

Added a dependency on typed_data.

Enhanced android_content.Intent#startActivity().

Fixed a build error in 0.6.0.

Fixed style nits with `flutter format`.

Updated the changelog and README.

Fixed build regression due to non-instantiable classes.

Defined android_bluetooth.Bluetooth*.* constants. (#1)

Removed all spurious files from Git:

    $ find . -name '*.iml' -delete
    $ find . -name .idea | xargs rm -rf

Fixed a bug in android_hardware.SensorManager.registerListener().