Split some files and add more documentation

src/lib.rs

@@ -1,10 +1,28 @@
+//! Crate for communicating with OBD-II (on-board diagnostics) interfaces on cars
+//!
+//! # Usage
+//! ```
+//! use obd2::{commands::Obd2DataRetrieval, device::Elm327, Obd2};
+//!
+//! fn main() -> Result<(), obd2::Error> {
+//!     let mut device = Obd2::<Elm327>::default();
+//!     println!("VIN: {}", device.get_vin()?);
+//!     Ok(())
+//! }
+//! ```
+
 #![forbid(unsafe_code)]
 
+pub mod commands;
+
 pub mod device;
 
+mod error;
+pub use error::Error;
+use error::Result;
+
 mod interface;
 pub use interface::Obd2;
 
 mod obd2_device;
-use obd2_device::Result;
-pub use obd2_device::{Error, Obd2Device};
+pub use obd2_device::Obd2Device;