Update to nom 7.0 @ master

Signed-off-by: Constantin Nickel <constantin.nickel@gmail.com>

Cargo.toml

@@ -15,7 +15,7 @@ license       = "MIT"
 name="tar"
 
 [dependencies]
-nom = { version = "6.2", default-features = false, features = ["alloc"] }
+nom = { default-features = false, features = ["alloc"], git = "https://github.com/Geal/nom.git", rev = "ef5e0bbc" }
 
 [badges]
 travis-ci = { repository = "Keruspe/tar-parser.rs" }