Pull in quote 1.0.4

Includes https://github.com/dtolnay/quote/pull/151 which will be used in
the implementation of type_id.
diff --git a/macro/Cargo.toml b/macro/Cargo.toml
index 4c2d423..18b46e5 100644
--- a/macro/Cargo.toml
+++ b/macro/Cargo.toml
@@ -13,7 +13,7 @@
 
 [dependencies]
 proc-macro2 = "1.0"
-quote = "1.0"
+quote = "1.0.4"
 syn = { version = "1.0", features = ["full"] }
 
 [dev-dependencies]