Add support for linux

[yinflying]

Change Some code to fit for LINUX
modify url_hinter.rb in line 50

Weechat.config_set_plugin(option, 'open' )

to

Weechat.config_set_plugin(option,'xdg-open')

modify url_hinter.rb in line 351

Weechat.string_remove_color(message.dup, '')

to

Weechat.string_remove_color(message.dup, '').force_encoding("UTF-8")