GPG doc updates.

This includes:

* publishing to a keyserver
* revocation
* setting the default signing key via lein
Add support for no_proxy environment variable

Closes #816.
Move Tiered Compilation to LEIN_JVM_OPTS and document.

Fixes #1111.
Move default :test-selectors to :leiningen/test profile.

Fixes #1099.
Merge pull request #1114 from joelittlejohn/system-no-proxy

Add support for no_proxy environment variable
Fix self-install dev heuristic to refuse to operate on a checkout.

Fixes #1106.
Use `file.separator` in pom path relativization.

Fixes #944 I think.
Add a note about testing the repl task.
Release 2.1.2
Back to 2.2.0-SNAPSHOT.
Argh; forgot NEWS for 2.1.2. Here it is.
Fix typo in sample project
Update docs with semantic change for profiles.d

Ref fa602e807bd772124d5ce00236d57f92bebf3818.
update tests template to :require from :use
Merge pull request #1115 from arrdem/patch-1

update tests template to :require from :use
same require update for the app template