* Simplify scrollbar refresh and measurement by using imperative DOM
manipulation instead of React to hide/show scrollbars.
* Rename `::performInitialMeasurement` to `::becameVisible`
* Break `::checkForVisibilityChange` out of `::pollDOM` and use it in
to check for the element becoming visible in `componentWillUpdate`.
* Don't rely on stored visibility state anywhere. Always check again.
This could potentially be cached for an update cycle but being wrong
about this is disastrous so I'm being conservative.
Considering that the entire Atom core team has ctrl-a bound to move to
the first character and it's also the the default behavior of Sublime,
this seems like a more sensible and useful default option even though
it deviates from text editing norms on OS X.
I got the following error when running `checkout-head-revision`:
```
Uncaught TypeError: undefined is not a function /Applications/Atom.app/Contents/Resources/app/src/editor-component.js:804
addCommandListeners.editor:checkout-head-revision /Applications/Atom.app/Contents/Resources/app/src/editor-component.js:804
(anonymous function) /Applications/Atom.app/Contents/Resources/app/src/editor-component.js:840
jQuery.event.dispatch /Applications/Atom.app/Contents/Resources/app/node_modules/space-pen/vendor/jquery.js:4676
elemData.handle /Applications/Atom.app/Contents/Resources/app/node_modules/space-pen/vendor/jquery.js:4360
module.exports.KeymapManager.dispatchCommandEvent /Applications/Atom.app/Contents/Resources/app/node_modules/atom-keymap/lib/keymap-manager.js:400
module.exports.KeymapManager.handleKeyboardEvent /Applications/Atom.app/Contents/Resources/app/node_modules/atom-keymap/lib/keymap-manager.js:181
module.exports.WindowEventHandler.onKeydown
```
It looks like it was caused by a bad merge conflict resolution in 0eaec57.
Test Plan:
Built new Atom and pressed `cmd-alt-z` and didn't get an error.
Looked at a side-by-side diff to check for any other merge issues:
```
git difftool -t opendiff 32e59ce..32e59ce^ src/editor-component.coffee
```
coffeelint.json had some rules set to ignore, but since #3116 was merged there
are no violations of these rules in the code anymore. Tighten up the rules to
prevent those kinds of errors from creeping back in.
Test Plan:
Lint executes without finding any errors
```
$ ./script/grunt coffeelint
Running "coffeelint:src" (coffeelint) task
>> 80 files lint free.
Running "coffeelint:build" (coffeelint) task
>> 23 files lint free.
Running "coffeelint:test" (coffeelint) task
>> 40 files lint free.
Done, without errors.
```
