Fixes #2506 - Extract autogrow feature from bugform and apply to comment

[Regaddi]

This PR fixes issue #2506

Proposed PR background

Please provide enough information so that others can review your pull request:
This change will add auto-expand functionality on the new comment textfield on an issue details page.

---

• I have read the Pull Request + Code Style Guidelines thoroughly.

[TravisBuddy]

Travis tests have failed

Hey @Regaddi,
Please read the following log in order to understand the failure reason.
It'll be awesome if you fix what's wrong and commit the changes.

1st Build

nosetests

Milestones are not initialized. Check logs.

npm run test:js -- --reporters="runner" --firefoxBinary=`which firefox`

> webcompat@ test:js /home/travis/build/webcompat/webcompat.com
> node ./tests/functional/_intern.js "--reporters=runner" "--firefoxBinary=/home/travis/firefox-58.0/firefox/firefox"

Error: 
        ======================================================
        Oops, something went wrong. Try restarting the server.
        Open another terminal and window type:
        npm run start:test
        or
        python run.py -t
        ======================================================
        
  at ClientRequest.<anonymous>  <tests/functional/lib/setup.js:55:9>
  at emitOne  <events.js:116:13>
  at ClientRequest.emit  <events.js:211:7>
  at Socket.socketErrorListener  <_http_client.js:387:9>
  at emitOne  <events.js:116:13>
  at Socket.emit  <events.js:211:7>
  at emitErrorNT  <internal/streams/destroy.js:64:8>
something bad happened inside intern.run()
{ Error: 
        ======================================================
        Oops, something went wrong. Try restarting the server.
        Open another terminal and window type:
        npm run start:test
        or
        python run.py -t
        ======================================================
        
    at ClientRequest.<anonymous> (/home/travis/build/webcompat/webcompat.com/tests/functional/lib/setup.js:55:9)
    at emitOne (events.js:116:13)
    at ClientRequest.emit (events.js:211:7)
    at Socket.socketErrorListener (_http_client.js:387:9)
    at emitOne (events.js:116:13)
    at Socket.emit (events.js:211:7)
    at emitErrorNT (internal/streams/destroy.js:64:8)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickCallback (internal/process/next_tick.js:180:9) reported: true }
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! webcompat@ test:js: `node ./tests/functional/_intern.js "--reporters=runner" "--firefoxBinary=/home/travis/firefox-58.0/firefox/firefox"`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the webcompat@ test:js script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/travis/.npm/_logs/2018-06-21T17_51_06_773Z-debug.log

[miketaylr]

Travis tests have failed

Blah, I need to figure out #2375...

[laghee]

Is the IO error after the sleep 2 script significant at all? (It's the same one that was blocking the windows install, but I'm not sure why it would be intermittent.)

[miketaylr]

oooo, crud. I need to make that directory if it doesn't already exist. Thanks @laghee!