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>
Add recipe for abc-mode
work around tramp loaddefs bug

tramp-loaddefs.el uses `tramp-verion' before it's defined, work around
this by loading trampver.el first.
tramp.rcp: little cleanup

remove :module from CVS times, and needless nesting in :build.
Merge pull request #1634 from npostavs/tramp-fixup

work around tramp bug
Merge pull request #649 from DarwinAwardWinner/doc-improvements

Doc improvements
Modify fsharp-mode recipe
replace flet with let+lambda+funcall

flet is marked obsolete in 24.3 resulting in quite a lot of annoying
messages. The intended replacement is cl-flet, but that is unavailable
in earlier emacsen, so we can't use that either.
Merge pull request #1638 from npostavs/no-flet

replace flet with let+lambda+funcall
Fix el-get-elpa-update-available-p for Emacs >24.3
Call package-initialize in el-get-elpa-update

Otherwise, `package-alist` is nil when `el-get-elpa-update-available-p`
is called, which yield another "Wrong type argument: arrayp, nil" error.
Comment why checking available-package
benchmark-init recipe
Merge pull request #1640 from dholm/recipe/benchmark-init

benchmark-init recipe
Remove :prepare clause
flyspell-lazy recipe