Fix Travis failures and publishing of builds.

Updates to the latest ember-dev which ensures that the git config
user.name and git config user.email values are present before calling
git cherry-pick. This is due to a recent change in git 1.8.5 which
requires the user information be present prior to a cherry-pick.

Travis accidentally reverted to using an older git version that does not
support the `--points-at` flag that we are using in `ember-dev`.

This forces the system to upgrade to the latest version.

Travis ticket for reference:
https://github.com/travis-ci/travis-ci/issues/1710.
[BUGFIX] Clean up findAllCache after unloading all records.
Merge pull request #1555 from abuiles/fix-unloadAll

[BUGFIX] Clean up findAllCache after unloading all records.
Merge pull request #1549 from rjackson/fix_publishing_of_builds

Fix Travis failures and publishing of builds.
Clean up the docs in system/model/attributes
- Documents the attributes and transformedAttributes static properties
- Documents the eachAttribute and eachTransformedAttribute static functions
- Fixes the docs for DS.attr so the website will no longer claim it lives in DS.Model
- Add example for DS.attr docs
Merge pull request #1558 from bmac/model-attributes-docs

Clean up the docs in system/model/attributes
add DS.Errors object