Remove echo '-s' flag

If you look at the files modified they used to contain `echo -n -s ...` however on the two systems I use (OSX 10.8 and Ubuntu 12.04) and from what I have read online, this does not exist.

    echo -n -s "hello world"

Produces `-s hello world` without a trailing newline. This affects all the themes and leaves a unsightly `-s` in the prompt.

I have been testing without the `-s` and everything seems fine, so if there is a reason for this you may want to put a test in somewhere and check when to use it.