Update documentation
Update documentation

* Rewrite and reorganise the README.

* Add more details about what software is installed, in particular the
  Vim plugins.

* Include information about the backup script.

sdillingham/dotfiles,seiryu9/dotfiles,nick-thompson/dotfiles,codfish/dotfiles,Gastove/dotfiles,seiryu9/dotfiles,saclark/dotfiles,micahwood/linux-dotfiles,necolas/dotfiles,senorflor/dotfiles,lgaechter/dotfiles,pertoyra/dotfiles,jmyser/dotfiles,intiocean/dotfiles,pmacom/dotfiles,SBoudrias/dotfiles,Stubby/dotfiles,micahwood/linux-dotfiles,bronxct1/dotfiles,micahwood/linux-dotfiles,micahwood/linux-dotfiles,micahwood/linux-dotfiles,bronxct1/dotfiles,codfish/dotfiles,SiTaggart/dotfiles,senorflor/linux-dotfiles,Stubby/dotfiles,marc0uk/dotfiles