Add path dep to metis-sys

so that changes to metis-sys can be tested locally.

Author: hhirtz

Cargo.toml

@@ -16,4 +16,4 @@ keywords = ["graph", "mesh", "matrix", "partitioning", "ordering"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-metis-sys = "0.1"
+metis-sys = { version = "0.1", path = "metis-sys" }