Make _showDropdown public

[ArjunDhar]

Hi,
thanks for such a nice plugin. Due to the input box (which is gr8 btw), the user has to click the flag to see the list. We have found idiot users find it hard to figure where to click.

What would be very useful, is some way to toggle() this via and external API. So developers can use their own UX to invoke your drop-down.

I saw the code and realized _showDropdown was one such method that could be public, or maybe have a pair showList(), hideList() that makes this possible.

If you feel its useful and is a quick fix for you, please do it. If not, Id be happy to try and contribute :)

[mrmarkfrench]

I'd be happy to accept a pull request that handles this.