flutter_dropdown 0.0.4

This does make Flutter Framework complicated dropdown button less complicated

[0.0.4] - Custom widget support.

• Custom widget support for dropdown menu items.

[0.0.3] - Any type dropdown button implementation.

• Create dropdown button for any data items.

[0.0.2] - String only dropdown button implementation.

• Create dropdown button for string items easily.

[0.0.1] - Simple dropdown button.

• Less complex boilerplate code for dropdown button.