Feature: Add options for tags_container_position

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I currently have an issue with how the tags are normally appeared on the live_select (on the top) so I decided to add another option called tags_container_position to allow user to decide whether the select should be on the top or the bottom of the text field.

Defaults to :top for original behaviour if the option isn't specified by the user.

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PR #120

Let me know if test is needed, and if so, guide me, much appreciated.

[maxmarcon]

Thanks but this is not needed. I explained why in the PR. Cheers!