Change ctrl-a binding to editor:move-to-first-character-of-line

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.
Elaborate getting a current working copy.

The `git checkout` step from #3098 got removed by some merge, so here it is again.
Upgrade to tree-view@0.120
Upgrade to language-gfm@0.50
Catch and log deactivate errors

Closes #3538
Merge pull request #3535 from Bengt/patch-1

Elaborate getting a current working copy.
:memo: :penguin: Tweak Linux instructions
:memo: Outdent ordered list
Upgrade to tree-view@0.121
Upgrade to markdown-preview@0.102
Upgrade to tree-view@0.122
Upgrade to find-and-replace@0.138
Merge pull request #3338 from atom/ns-change-ctrl-a-binding

Change ctrl-a binding to editor:move-to-first-character-of-line on Mac
Upgrade UI themes to fix tabs
Memoize comment scope selector
Upgrade to tree-view@0.123
Rename editor.softWrapped config option back to editor.softWrap
Rename editor:toggle-soft-wrapped back to editor:toggle-soft-wrap
Merge pull request #3545 from atom/ns-revert-soft-wrapped

Rename soft-wrapped back to soft-wrap
Upgrade keybinding resolver to fix deprecation warnings in specs