refactor(builder): simplify sed substitution

The `perl | sed` commands used previously were to remove single quotes
from the string. This sed replacement greatly simplifies that logic.
feat(builder): build apps from more than master

Previously, the builder would completely disregard any pushes from
a branch other than master. This moves the builder command into
a post-receive hook, such that we can reference the branch that
is being pushed to the repository and send that to the builder.

For some reason, this PR also gives us Heroku compatibility on
issue #736, so this PR kills two birds with one stone.

TESTING: To test, we need to successfully push an app from a branch
other than master. To do that, run the following:

    $ make -C builder build restart
    $ cd /tmp
    $ git clone https://github.com/opdemand/example-perl && cd example-perl
    $ git checkout -b test-branch
    $ deis create
    $ git push deis test-branch

To test for the #736 ninja fix, try pushing again. You should see a
"Everything up-to-date" message displayed on your screen, and no
push should occur.

fixes #975, #736
fix(contrib): revert seed hosts for CDN workaround

This reverts commit d3dfa376d86ffcbbbcab8211edb161b4cfde2d72.
chore(controller): remove unused coveragerc

the real coveragerc exists in the controller project.
test(controller): remove scheduler from coverage

The scheduler is not something we can easily test at the moment,
so let's remove it from our test coverage.
Merge pull request #1004 from deis/975-more-than-master

feat(builder): build apps from more than master
Merge pull request #1013 from deis/remove-cdn-workaround

fix(contrib): revert seed hosts for CDN workaround
Merge pull request #1014 from deis/coverage

test(controller): fix up coverage
feat(Vagrantfile) Default to a 3 node cluster