Shut up cask

Using the new `shut-up` macro from https://github.com/rejeep/shut-up.el/pull/2, I'm able to catch almost all output in this branch.

I've also changed error handling to include the output of package.el, whenever an error occurs.  Note that this **excludes** byte compilation errors and warnings, because these aren't consider as errors by package.el.

Some output still gets through, though:

```
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/archives/gnu/archive-contents
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/archives/melpa/archive-contents
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/epl-20140102.211/epl.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/epl-20140102.211/epl-autoloads.el
Making version-control local to epl-autoloads.el while let-bound!
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/epl-20140102.211/epl-autoloads.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/epl-20140102.211/epl-pkg.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/dash-20140119.955/dash.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/dash-20140119.955/dash-autoloads.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/dash-20140119.955/dash-autoloads.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/dash-20140119.955/dash-pkg.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/s-20131223.944/s.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/s-20131223.944/s-autoloads.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/s-20131223.944/s-autoloads.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/s-20131223.944/s-pkg.el
Wrote /Users/swiesner/.cask/.cask/24.3.50.1/elpa/f-20131225.721/f.el
[…]
```

These `Wrote […]` come from `write-region`, I presume, which is implemented in C.  I didn't look at its source code, but I am afraid, that the chance of catching these is rather low.

Regarding the `Making version-control […]` message, I have no clue where that comes from and how to catch it.  Likely, it's from the interpreter, and also straight from C, giving us no chance to catch it.