Relative imports

When including the the resulting Julia files from a.proto and b.proto inside a Julia module Julia complains that it's unable to locate Module A.  Using a relative import when building the Julia files fixes this issue however may not be the desired behaviour in all cases.
generated Julia code:

```Julia
module A


using ProtoBuf
import ProtoBuf.meta

type Description
    id::String
    name::String
    date::Float64
    Description() = (o=new(); fillunset(o); o)
end #type Description
meta(t::Type{Description}) = meta(t, Symbol[:id,:name,:date], Int[], Dict{Symbol,Any}())

export Description
export meta
end # module A
```