Update home dependencies to v0.5

This home's release remove support for the old `.multirust`
directory. Also it fixes rustup_home and cargo_home implementation
when corresponding environment variables are absolute paths.

Author: tesuji

Cargo.toml

@@ -35,7 +35,7 @@ git2 = "0.10.0"
 git2-curl = "0.11.0"
 glob = "0.3.0"
 hex = "0.3"
-home = "0.4.2"
+home = "0.5"
 ignore = "0.4.7"
 lazy_static = "1.2.0"
 jobserver = "0.1.13"