install: Use git submodules for vim plugins.
install: Remove the vim plugin installation.

These are now submodules.
install: Install pathogen via submodule.

It used to be part of the install.sh script.
install: Remove pathogen from the install script.
install: Break dockerfile vim syntax into separate script.
install: Move the zenburn color scheme into a submodule.
install: Remove unnecessary install code for zenburn.
install: Set up tools as submodules.
Merge branch 'use_git_submodules'

This branch turns a lot of the git clone commands from install.sh into
submodules. This way I can essentially get git to handle the extra repos
for me.