Switch back to using NamedTuples package (#75)

* Switch back to using NamedTuples package

* Remove current_module

REQUIRE

@@ -2,3 +2,4 @@ julia 0.6
 WeakRefStrings 0.4.0
 Missings
 Compat 0.59
+NamedTuples 4.0.2

src/DataStreams.jl

@@ -484,18 +484,36 @@ end
 datatype(T) = Core.eval(parentmodule(Base.unwrap_unionall(T)), nameof(T))
 
 @static if !isdefined(Core, :NamedTuple)
-include("nt.jl")
-using .NamedTuples
+using NamedTuples
 function Base.get(f::Function, nt::NamedTuple, k)
     return haskey(nt, k) ? nt[k] : f()
 end
+
 else
 macro NT(args...)
     return esc(:(($(args...),)))
 end
 end
 export @NT
 
+const ColNT = Ref{Any}()
+const ColNT2 = Ref{Any}()
+
+function __init__()
+    ColNT[] = @static if VERSION < v"0.7.0-DEV.2738"
+        nt = NamedTuples.create_namedtuple_type([:col])
+        x->nt(x...)
+    else
+        NamedTuple{(:col,)}
+    end
+    ColNT2[] = @static if VERSION < v"0.7.0-DEV.2738"
+        nt2 = NamedTuples.create_namedtuple_type([:name, :compute, :computeargs])
+        x->nt2(x...)
+    else
+        NamedTuple{(:name, :compute, :computeargs)}
+    end
+end
+
 include("namedtuples.jl")
 include("query.jl")