haddock-library: require GHC >= 7.4
haddock-library: require GHC >= 7.4

`Data.Monoid.<>` was added in base-4.5/GHC-7.4

Closes #394

Signed-off-by: Mateusz Kowalczyk <eefa6dfc1eac2904477d70db04ec6889dd790721@fuuzetsu.co.uk>

adamse/haddock,idontgetoutmuch/haddock,Helkafen/haddock,adamse/haddock,Helkafen/haddock,sboosali/haddock,lamefun/haddock,niteria/haddock,Fuuzetsu/haddock,Acidburn0zzz/haddock,Acidburn0zzz/haddock,beni55/haddock,adamse/haddock,Fuuzetsu/haddock,Helkafen/haddock,Fuuzetsu/haddock,esmolanka/haddock,mrhania/haddock,beni55/haddock,lamefun/haddock,lamefun/haddock,niteria/haddock,esmolanka/haddock,beni55/haddock,Fuuzetsu/haddock,randen/haddock,mrhania/haddock,haskell/haddock,haskell/haddock,randen/haddock,esmolanka/haddock,haskell/haddock,haskell/haddock,niteria/haddock,Acidburn0zzz/haddock,randen/haddock,idontgetoutmuch/haddock,sboosali/haddock,sboosali/haddock,haskell/haddock,idontgetoutmuch/haddock,mrhania/haddock