Refactoring

validate boolean attributes

Default branch auto-discovery

Unused routes removed

That was the only place it was used.

As a last resort it was calling a method that didn't exist. Woops!

default_branch now defaults to nil, not 'master'. It will be set after the first
push by discover_default_branch.

Refactor the project clone panel

I have no earthly idea what this file was for, but I couldn't find it being
rendered anywhere.

Replaces two calls that this method simplifies

Add tmp/.gitkeep file to ensure tmp folder exists on clone

Clean up doc/installation.md

Closes #939

The install guide lists it as a requirement, so we might as well have it
by default.