Don't auto-install python-mode anymore

It's part of Emacs 24.3 now
Add prelude-switch-to-previous-buffer
Add key chord for prelude-switch-to-previous-buffer
Merge pull request #303 from lukerandall/add-switch-to-previous-buffer

Add prelude-last-buffer
Add smex and ido-ubiquitous for better `M-x`
upgrade dash to 1.2
Merge pull request #308 from marivas/fix-flycheck-error

upgrade dash to 1.2
Don't use dash.el during package init
Merge branch 'master' of https://github.com/bbatsov/prelude
Correct the packages alphabetical order
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Don't use dash.el during package init
  upgrade dash to 1.2
  Add key chord for prelude-switch-to-previous-buffer
  Add prelude-switch-to-previous-buffer
  Don't auto-install python-mode anymore
Restore compatibility with Emacs 24.2
Merge pull request #305 from toctan/master

Add smex and ido-ubiquitous for better `M-x`
A couple of minor improvements
Add some missing docstrings
Shorten the names displayed in prelude-recentf-ido-find-file
Don't try edit dired buffer as root
Fix indentation
Merge pull request #310 from lukerandall/dont-sudo-dired

Don't try edit dired buffer as root
Extract prelude-start-or-switch-to