Update required cylinder version to 0.2.1
This is required because libsplinter makes use of features added in
0.2.1 that were not present in 0.2.0.
@@ -36,7 +36,7 @@ awc = { version = "0.2", optional = true }
bcrypt = {version = "0.6", optional = true}
byteorder = "1"
crossbeam-channel = "0.3"
-cylinder = "0.2"
+cylinder = "0.2.1"
diesel = { version = "1.0", features = ["r2d2", "serde_json"], optional = true }
diesel_migrations = { version = "1.4", optional = true }
futures = { version = "0.1", optional = true }
