Allow heapsize 0.4

Author: Eijebong

Cargo.toml

@@ -33,7 +33,7 @@ lazy_static = "0.2"
 serde = "0.9"
 phf_shared = "0.7.4"
 debug_unreachable = "0.1.1"
-heapsize = { version = "0.3", optional = true }
+heapsize = { version = ">= 0.3, < 0.5", optional = true }
 string_cache_shared = {path = "./shared", version = "0.3"}
 
 [dev-dependencies]