Use a more recent vala-mode than ELPA's
Remove obsolete magithub

See magit issue: https://github.com/milkypostman/melpa/issues/1126
Update dtrt-indent recipe to github; point temporarily at a working fork
Fix a small typo in README.md
Add instructions on replicating a configuration

Use Dimitri's code from #1548

Also add a note to the `init-` packages section about existing
packages.
Merge pull request #1556 from rrthomas/master

Use a more recent vala-mode than ELPA's; remove magithub; fix dtrt-indent; add instructions for replicating a configuration