Update install.sh

sed --version and date --version do not work on OSX. Instead i used [this method](http://stackoverflow.com/questions/592620/how-to-check-if-a-program-exists-from-a-bash-script/677212#677212) to determine if these tools were installed.
fixed syntax error
tput colors instead
Merge pull request #3 from mikedfunk/tput-colors

Tput colors