O2_install.sh needs to verify the current $PATH value

Running `O2_install.sh` multiple times will continuously add lines to `~/.bash_profile`. The script should first ensure that `PATH` doesn't already contain the location of mcmicro before adding it.

Additionally, the instructions do not accurately reflect the location of the script. Need to change `/n/groups/lsp/cycif/mcmicro/O2_install.sh` to `/n/groups/lsp/cycif/mcmicro/bin/O2_install.sh`