docs: Make the build reproducible
docs: Make the build reproducible

By setting today's date to the current year, the manpage output doesn't
vary with the day the manpage was built.

Having reproducible builds is a goal for Debian stretch.

dbrgn/mopidy,tkem/mopidy,mokieyue/mopidy,bacontext/mopidy,diandiankan/mopidy,mokieyue/mopidy,hkariti/mopidy,SuperStarPL/mopidy,quartz55/mopidy,mokieyue/mopidy,mopidy/mopidy,jmarsik/mopidy,SuperStarPL/mopidy,vrs01/mopidy,glogiotatidis/mopidy,swak/mopidy,mopidy/mopidy,dbrgn/mopidy,kingosticks/mopidy,ali/mopidy,rawdlite/mopidy,vrs01/mopidy,bacontext/mopidy,SuperStarPL/mopidy,rawdlite/mopidy,glogiotatidis/mopidy,jcass77/mopidy,ali/mopidy,tkem/mopidy,jcass77/mopidy,jmarsik/mopidy,mopidy/mopidy,jmarsik/mopidy,quartz55/mopidy,ZenithDK/mopidy,pacificIT/mopidy,kingosticks/mopidy,bacontext/mopidy,glogiotatidis/mopidy,jodal/mopidy,swak/mopidy,swak/mopidy,tkem/mopidy,hkariti/mopidy,dbrgn/mopidy,quartz55/mopidy,swak/mopidy,glogiotatidis/mopidy,ZenithDK/mopidy,hkariti/mopidy,bencevans/mopidy,bencevans/mopidy,vrs01/mopidy,diandiankan/mopidy,pacificIT/mopidy,vrs01/mopidy,ali/mopidy,bacontext/mopidy,mokieyue/mopidy,pacificIT/mopidy,adamcik/mopidy,quartz55/mopidy,kingosticks/mopidy,ali/mopidy,rawdlite/mopidy,adamcik/mopidy,hkariti/mopidy,jcass77/mopidy,SuperStarPL/mopidy,tkem/mopidy,jmarsik/mopidy,jodal/mopidy,dbrgn/mopidy,rawdlite/mopidy,ZenithDK/mopidy,adamcik/mopidy,diandiankan/mopidy,diandiankan/mopidy,bencevans/mopidy,ZenithDK/mopidy,bencevans/mopidy,jodal/mopidy,pacificIT/mopidy