add unique string to generated git-vars file

this way it's easier to safely remove it later
clean up vim housekeeping files
add removal option
keep OS-specific profiles but not machine-locals

machine-local profiles are still supported and take the form:
"~/.hostname.profile"
clean up screen cfg
move zsh history housekeeping into zsh
ignore development files when installing
rm housekeeping files on uninstall
version ssh config, not ssh dir itself
add link to installation screencast
update youtube link to HD version with subtitles on
add screencast poster image
Update README.md
rm push: simple; breaks older git versions