Rename Ty -> Type

Rust source code does not abbreviate type -> ty (the way it abbreviates impl and
mod, for example). This commit updates the naming in syn to reflect that.
diff --git a/src/data.rs b/src/data.rs
index 56004a1..7c97311 100644
--- a/src/data.rs
+++ b/src/data.rs
@@ -70,7 +70,7 @@
         pub attrs: Vec<Attribute>,
 
         /// Type of the field.
-        pub ty: Ty,
+        pub ty: Type,
 
         pub colon_token: Option<Token![:]>,
     }
@@ -116,7 +116,7 @@
             vis: syn!(Visibility) >>
             id: syn!(Ident) >>
             colon: punct!(:) >>
-            ty: syn!(Ty) >>
+            ty: syn!(Type) >>
             (Field {
                 ident: Some(id),
                 vis: vis,
@@ -129,7 +129,7 @@
         named!(pub parse_tuple -> Self, do_parse!(
             attrs: many0!(call!(Attribute::parse_outer)) >>
             vis: syn!(Visibility) >>
-            ty: syn!(Ty) >>
+            ty: syn!(Type) >>
             (Field {
                 ident: None,
                 colon_token: None,