update gitconfig for ubuntu
script/bootstrap: update for ubuntu

- remove auto gitconfig generation
- remove auto install dependencies (homebrew)
edit gitconfig

- set push.default to 'nothing' because 'simple' isn't supported
update readme

- main differences between osx branch and ubuntu branch
- add misc note about changing default text editor
update homebrew directory and script

- renamed the homebrew directory to apt-get and edited the install
  script so that it would use apt-get to install all the utilities I'd
  like (git, htop, etc)