added Num a to type signature in order to fix ambiguity error given by compiler

When running Makefile the compiler complains about the type signature for boolBit. See below
   
   ghc -O2 --make Main.hs -o Main
   [1 of 6] Compiling CPU.Types        ( CPU/Types.hs, CPU/Types.o )
   [2 of 6] Compiling Helpers          ( Helpers.hs, Helpers.o )

Helpers.hs:34:17:
    Could not deduce (Num a) arising from the literal `1'
    from the context (Bits a)
      bound by the type signature for boolBit :: Bits a => Bool -> a
      at Helpers.hs:33:12-30
    Possible fix:
      add (Num a) to the context of
        the type signature for boolBit :: Bits a => Bool -> a
    In the expression: 1
    In an equation for `boolBit': boolBit True = 1
make: *** [all] Error 1

I took the advice of the compiler and added Num a.