Adding documentation

src/args/posarg.rs

@@ -1,3 +1,11 @@
+/// PosArg represents a positional argument, i.e. one that isn't preceded 
+/// by a `-` or `--`. 
+/// Example: 
+/// ```sh
+/// $ myprog some_file
+/// ```
+/// where `some_file` is the first positional argument to `myprog`
+/// **NOTE:** The index starts at `1` **NOT** `0`
 pub struct PosArg {
     pub name: &'static str,
     pub help: Option<&'static str>,

src/lib.rs

@@ -1,5 +1,11 @@
+#![crate_id = "clap"]
+#![crate_type= "lib"]
+
 #![feature(collections, core, libc, env)]
 
+//! A simply library for parsing command line arguments when writing 
+//! command line applications.
+
 pub use argmatches::ArgMatches;
 pub use arg::Arg;
 pub use app::App;