Add structopt for arg parsing

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

Cargo.toml

@@ -9,6 +9,7 @@ build = "build.rs"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+structopt = "0.3"
 bitflags = "1"
 byteorder = "1"
 lazy_static = "1"