Bump heapsize to at least 0.4.1 (relicensed)

Heapsize was released as `0.4.1` to reflect the license change. (servo/heapsize#85).

Fixes #317.

Author: theduke

Cargo.toml

@@ -41,7 +41,7 @@ heap_size = ["heapsize"]
 
 [dependencies]
 encoding = {version = "0.2", optional = true}
-heapsize = {version = ">=0.1.1, <0.5", optional = true}
+heapsize = {version = ">=0.4.1, <0.5", optional = true}
 idna = { version = "0.1.0", path = "./idna" }
 matches = "0.1"
 percent-encoding = { version = "1.0.0", path = "./percent_encoding" }