Issue title: really long completions get truncated 
 Issue body: ![image](https://cloud.githubusercontent.com/assets/1366709/9313631/f235d5e4-44f1-11e5-9725-d101257bc933.png)

 Comments: 
 Comment 0: I was hopeful of an event (onShowAutocomplete or something) I could hook into so that the width could be set. No luck unfortunately.

Although not the most robust solution, I could increase the `width` property for the `.ace_autocomplete` selector. Its value is 280px.
{'source': 'GithubIssues', 'repo_name_with_owner': 'att/rcloud', 'issue_id': 101489960, 'repo_stars': 424.0}