Implements multiple selections clipboard paste

Includes:

  - Passing the selection index in the `Editor::mutateSelectedText`
method callback
  - Storing all the selections content on many calls of
`Selection::copy` with `maintainClipboard = true` in a metadata
`selections` array
  - Handling clipboard with a `selections` metadata in
the`Editor::pasteText` method
:lipstick: Fix typo in pasteText method comments
Allow newer version of `nodejs`
Adds specs for multi selections clipboard handling
Don't use comment lines to determine soft/hard tabs.

Closes atom/language-php#24
Closes #1733
Upgrade to text-buffer@2.2.1
Merge remote-tracking branch 'origin/master' into cj-tabs-be-weird
Wordsmith the readme
fix io typo
This doesn't need to change.
Apply @probablycorey's suggestions
Fix Windows build instructions
Make atom build behind firewalls

This is to get `npm install` to work behind firewalls where `git://` is blocked.
+FreeBSD, -bullshit

Signed-off-by: Cthulhux <zeug@tuxproject.de>
Shift backspace keymap

Within windows build shift-backspace currently does nothing. Behaviour
untested in linux (perhaps linux.cson should be modified too?)
Merge remote-tracking branch 'origin/master' into cj-tabs-be-weird

Conflicts:
	package.json
:lipstick: Replace have with has in spec description
:lipstick: Harmonize lineForRow calls in specs
:lipstick: Use skinny arrow instead
:sweat_smile: Forgot to remove the test focus