Prevent focus loss on double click without breaking single click focus

Previously, we stopped propagation on mousedown events to prevent
certain cases where focus was being lost after double clicking to select
a word.

Unfortunately, this also broke the ability to focus the editor by
clicking it. When investigating this, I noticed that whenever we lost
focus, the target of the mousedown event was always the cursor. So I
tried setting `pointer-events: none` on cursors and can no longer
reproduce the double-click issue.

/cc @probablycorey
Upgrade to grunt-download-atom-shell@0.8.0
Upgrade to atom-shell@0.13.0
Support generating i386 deb file.
:memo: Mention 32bit arch is supported.
Merge pull request #2524 from atom/atom-shell-v0.13.0

Support 32bit build on Linux
Add debugging guide to list of guides
Upgrade space-pen now that problem with 3.2.4 is fixed
Classic copy/paste added to Linux and Win32

Ctrl+Insert: Copy
Shift+Insert: Paste
Merge pull request #2561 from batjko/master

Add classic copy/paste to Linux and Win32 keymaps
Upgrade to first-mate 1.7
Upgrade to tree-view@0.98
0.103.0
Upgrade to find-and-replace@0.114.0
Remove script/install-cli

The CommandInstaller class now has native module dependencies that are
compiled with apm so invoking it directly from node is no longer possible.

This can still be done using the grunt install task.

Closes #2555
fold classes work
Beginning of decorations
Renders decoration changes.
Rendering decorations works well.

Also specs.
Debounce the rendering of decorations