add enable() method to Typeahead
add enable() method to Typeahead

Summary: adds an enable() method to Typeahead.  Use case is the following: I have a tokenizer and when a certain class of tokens is selected I want to disable the typeahead.  When those tokens are removed I want to re-enable the typeahead.

Test Plan: Implemented tokenizer with this behavior

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3617

phacility/javelin,phacility/javelin,phacility/javelin,phacility/javelin,phacility/javelin