Better documentation of :checksum and :checkout properties

* Explain the difference between :checkout and :checksum
* Document that hg method now supports these properties
document 719264d (even though it isn't merged yet)
Document that checksums may not be abbreviated

As requested in #626.
In hg, "checkout" is properly spelled "update"
methods/el-get-github: change the default url type to https

All git repositories should be fetched over HTTPS by default, to allow
authenticated pushes to the user's own repositories.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Fix typo , by adding " " to :pkgname
Added pythonbrew-mini
Add failing test for #1454
Fix #1454 by requiring package.el eagerly

Just adding "(require 'package)" to "el-get-elpa-package-directory"
fixes this bug, because by the time any elpa package is being installed
or fetched, package.el has to be available, so all we have to do is load
it if it hasn't already been loaded.
Don't overwrite existing "package-archives" value

Instead, we add the archives we want without blowing away any others.
Point `workgroups` recipe to new repository

`tlh/workgroups` has been dead for a while now.
Merge pull request #1464 from vedang/fix-workgroups-rcp

Point `workgroups` recipe to new repository
Add :depends to ac-slime.rcp
Merge pull request #1466 from xiaohanyu/fix-ac-slime-depends

Add :depends to ac-slime.rcp
fix el-get-remove-autoloads for emacs != 24.3

Instead of tricking autoload-find-destination to do what we want, pull
out the relevant bits of code that do removal.

Using autoload-find-destination works in emacs 24.3 apparently because
of a bug: file-attributes returns a 4 integer list for time, but the
autoload function expects the old 2 integer format.  In 24.2 where
file-attributes still returns 2 integers, the autoload section is
considered up to date and is not removed.
Don't update popup-el submodule

Because its submodule is used only for tests

  auto-complete/popup-el#49
Set submodule keyword to 't' for yasnippet recipe.

Yasnippet has seperate its snippet and scripts to two other seperate repos.
We need the submodules to make yasnippet work as expected by default.
Merge pull request #1474 from xiaohanyu/yasnippet-git-submodule

New build step for yasnippet recipe.
Merge pull request #1470 from syohex/disable-popup-git-submodule

Don't update popup-el submodule
Merge pull request #1469 from npostavs/autoload-remove3

fix el-get-remove-autoloads for emacs != 24.3