Move topsorting to Mix.Deps.Umbrella
Update CHANGELOG
Just skip loadpaths on deps.update and deps.get
Precalculate the manager for unfetched dependencies
Revert "Fix status code in mix test"

This reverts commit 4fc3fc11de37dff41f439140e027a7743e00dc3e.

We want to run all mix umbrella projects together, because
all their apps are booted together and we should not pretend
otherwise.
Improve error message for overriden deps
Improve syntax error on invalid calls

Closes #1847
Check the elixir req for dependencies too

Also streamline the workflow for deps.get and deps.update.
Add a workaround for Mix deps.get and deps.umbrella what was not loading path deps

This will be properly fixed in a couple days once we move
to _build directories.
No need to support @recursive :both anymore
Do not fetch the manager before the repo is available
Add a test case ensuring managers are not set eagerly
Move unicode from priv/ to unicode/
Do not allow duplicated projects to be pushed onto the stack

Closes #1846
Remove duplication in deps.compile