Fix high cpu usage if stdin is /dev/null
Fix high cpu usage if stdin is /dev/null

See issue #71.

Vi1i/pianobarfly,bmbove/pianobar-save,Vi1i/pianobarfly,twahlfeld/pianobar,tchajed/pianobar,twahlfeld/pianobar,bmbove/pianobar-save,Vi1i/pianobarfly,gnowxilef/pianobar,johndeeney/pianobar,gnowxilef/pianobar,gnowxilef/pianobar,johndeeney/pianobar,DavidZemon/pianobar,tchajed/pianobar,tchajed/pianobar,johndeeney/pianobar,DavidZemon/pianobar,johndeeney/pianobar,gnowxilef/pianobar,tchajed/pianobar,bmbove/pianobar-save,johnso51/pianobar,johnso51/pianobar,Vi1i/pianobarfly,johndeeney/pianobar,DavidZemon/pianobar,gnowxilef/pianobar,DavidZemon/pianobar,DavidZemon/pianobar,bmbove/pianobar-save,tchajed/pianobar,DavidZemon/pianobar,johnso51/pianobar,johnso51/pianobar,johnso51/pianobar,bmbove/pianobar-save,Vi1i/pianobarfly,johndeeney/pianobar,gnowxilef/pianobar,johnso51/pianobar,tchajed/pianobar,twahlfeld/pianobar,twahlfeld/pianobar,twahlfeld/pianobar,twahlfeld/pianobar