Move usage to the top to decrease latency

reco/royfit.jl

 #!/usr/bin/env julia
+
+if length(ARGS) < 2
+    println("Usage: ./live_royfit.jl LIGIER_HOST LIGIER_PORT")
+    exit(1)
+end
+
 println("Initialising libraries, this may take a minute...")
 using Sockets
 using NeRCA
@@ -8,12 +14,6 @@ using Dates
 using Measures
 GR.inline("png")
 
-if length(ARGS) < 2
-    println("Usage: ./live_royfit.jl LIGIER_HOST LIGIER_PORT")
-    exit(1)
-end
-
-
 const calib = NeRCA.read_calibration("/data/latest.detx")
 const LIGIER_HOST = getalladdrinfo(ARGS[1])[1]
 const LIGIER_PORT = parse(Int, ARGS[2])