only allow one instance

Cargo.toml

@@ -7,13 +7,8 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
-failure = "0.1"
 swayipc = {version = "2.7.0", features = [ "event_stream"]}
-
-#[dependencies.swayipc]
-#features = ["async", "event_stream"]
+single-instance = "0.1.2"
 
 [packaging]
 depends = ["sway"]