unwrap values during fetch

fetching a value with #fetch a proc might be set to the specified key,
in order to unwrap all procs and only return the underlying value,
value.call is performed as long as it does not return any new proc
objects (e.g. it does not repond to :call any more).

fixes #859
Recapped an issue as a PR

fixed #694 Just listed out the other two ways to implement this as discussed in the issue.
Add CodersClan to Capistrano
Added space between ## and Support
Merge pull request #879 from CodersClan/master

Add CodersClan to Capistrano
Added support for subversion by extending pre-existing scm strategy, as noted in new documentation.
Update README with 3.1 version
Merge pull request #880 from alepore/patch-1

Update README with 3.1 version
Revert ":panda_face: 857: Load tasks from the deploy.rb"

This reverts commit a5b76f782a11b191aff87e52734202c949dbbb3b.

This commit which looked to solve #867 / #857 has caused regressions in
other areas - I'm reverting this commit because the solution to the original
issue of tasks declared in `config/deploy.rb` not appearing in the list of
tasks returned by `cap -T` is to move those tasks into
`lib/capistrano/tasks` and load them from the Capfile (as per the
generated template). Defining tasks in a configuration file may work as
far as running the tasks goes, but it's not the intended use for that
file.

This commit closes #887, and I suspect #881 as well.
Add CodersClan to Contributing + other fixes

Fixed Stack Overflow and Mailing List links.
Add parameters to CodersClan links
Using `.rake` extension instead of `.cap`
In tests and default templates
Merge pull request #900 from kirs/rake-instead-of-cap

Using `.rake` extension instead of `.cap`.
Merge pull request #893 from Orchestrator81/master

Add CodersClan to Contributing + other fixes
Delete capistrano-public_cert.pem
Merge pull request #873 from signedbyte/patch-1

Recapped an issue as a PR.
Merge pull request #872 from Kriechi/fix_fetch_procs

Unwrap values during fetch.
Merge pull request #838 from chendrix/master

Added support for subversion by extending pre-existing scm strategy