Fix a bug causeing `gist -c` fails for xsel users.

Unlike `xclip`, calling `xsel` without any argument outputs the
selection.
In other words, `xclip` defaults to `xclip -i`,
but xsel` defaults to `xsel -o`.

Thus we should use `xsel -i` instead of `xsel` for copying the url
to clipboard.
Merge branch 'master' of github.com:weakish/gist
bump version