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.
Better autodetection of Soft Tabs.

Check for the presence of a space, instead of the absence of a tab.
This ensures that Soft Tabs will not be activated on a file that (for
example) starts with a BOM or something, but is otherwise full of hard
tabs.
Support built-in context menu items
Add cut/copy/paste built-in context menu items
:penguin: Move settings items to Edit menu

Closes #2467
Upgrade to welcome@0.18
Log location of created .deb file
:penguin: Set installedSize value in control file

Closes #2183
installSize -> installedSize
Split on whitespace
Upgrade to tabs@0.50
Update find-and-replace
merge latest upstream master
updated regex in usesSoftTabs to only look for Tab and Space
Added linux open-folder keybind.
Moved application:open-dev to `ctrl-alt-o`
Use public getters instead of properties in pane-spec
:lipstick: simplify assignment using coffeescript magic
Start adding event subscription methods to pane

This branch uses EventKit, an ultra-simple library for implementing
events. The object implementing the methods maintains its own emitter
object rather than doing a mixin like Emissary encourages. This will
make it easier for us to deprecate ::on on the object itself. Unlike
emissary, the EventKit Emitter implements a super minimalistic API that
only allows one value to be emitted and always returns a Disposable
from subscriptions.
Add Pane::onDidMoveItem()
Add spec for onDidRemoveItem observers when moving items to other panes