Fix bug with getproperty in @byrow

[pdeffebach]

julia> df = DataFrame(a = [1, 2], b = [3, 4]);

julia> @byrow df begin
       :a = mean(df.b)
       end
ERROR: syntax: invalid syntax "df.(##255[row])" around REPL[4]:2

This is a problem because QuoteNodes show up in getproperty calls.

julia> dump(:(d.x))
Expr
  head: Symbol .
  args: Array{Any}((2,))
    1: Symbol d
    2: QuoteNode
      value: Symbol x

This is a super easy fix, I think. replace_dotted already exists for other operations which cleans getproperty calls.