[BezierEditor] Fix fadeout issue

[marcelgerber]

Steps to reproduce the issue, introduced by #7235:

1. Start an Inline Timing Function Editor
2. Make the function invalid, like cubic-bezier(1.000001, 0, 0, 0)
3. Make it valid again
4. Make some other valid changes (like deleting the additional zeros) while the fadeout is still running

Result: The hint is immediately hidden
Expected: The fadeout should continue

This PR makes the code a bit cleaner (using editor.hint object for everything that has to do with the hint) and uses .hide(), suggested by @zaggino.

[redmunds]

@SAplayer I could review pull requests faster if the branch names weren't so long :)

[marcelgerber]

@redmunds I'll try to use a shorter one next time ;)

[njx]

@redmunds Try https://github.com/defunkt/hub - then you can do things like hub checkout https://github.com/adobe/brackets/pull/7248

[peterflynn]

I always just copy-paste the branch name from the top of the PR into the terminal, personally :-) Or you can click the "command line" link at bottom (next to the merge button) and copy the full command line to the clipboard in 1 click...

[redmunds]

Looks good. Merging.