create ~/.profile if it doesn't exist and the next line of PATH is useless.
fix typo in README
let's support zsh for real :)

`~/.profile` is not used for zsh FYI.

Instead, `~/.zprofile` is used, but this file is only for login shell. We need
to support interactive shell as well (I use PuTTY a lot...)

I understand that there's always a workaround for zsh users to source the
~/.profile, but that requires an extra step for users. Using this code would
make zsh users' life easier. :D
fix typo in doc manual
Merge pull request #58 from guanqun/master

a few fixes about the install script