fix ignoring hash in URL

vimproc's parser seems to treat # as a comment.  This is a problem when
I open URL which contains hash.
For example, when I execute `:OpenBrowser https://github.com/rhysd/dotfiles/blob/master/vimrc#L1`,https://github.com/rhysd/dotfiles/blob/master/vimrc would be opened because
'#L1' would be treated as a comment.

I've fixed this problem by escaping '#' like '\#'.
Merge pull request #40 from rhysd/fix/hash

Fixed ignoring hash in URL