Go back to Solarized Light

Zenburn was just not my favorite

This reverts commit 13e9292841a649fe94a63d5706ac068d3d372b4f.
Improve smooth scrolling
Fix compilation warnings
Fix usage of GNU ls on OS X

Do not mangle `exec-path`, but rather use the `gls` executable.
Fix compilation warnings
Improve Magit experience

Ask to set upstream branches on first push, and improve naming of remote
tracking branches.
Remove dead auto-complete configuration
Improve ERT coding

Fix font-locking and indentation of ERT test declarations.