extend readme a bit

README.md

@@ -1,6 +1,6 @@
 # Ivory
 
-Writing php extensions in rust
+Writing php extensions in rust made easy
 
 ## Usage
 
@@ -8,14 +8,28 @@ Writing php extensions in rust
 use ivory::{ivory_export, ivory_module};
 use ivory::externs::printf;
 
+/// Basic methods
+#[ivory_export]
+fn hello_world() {
+    printf("Hello world, Rust!");
+}
+
+/// Automatically casts function arguments for php
 #[ivory_export]
 fn hello_other(other: String) {
     printf(format!("Hello {}", other));
 }
 
+/// And casts return types back to php
 #[ivory_export]
-fn hello_world() {
-    printf("Hello world, Rust!");
+fn add_one(input: i64) -> i64 {
+    input + 1
+}
+
+/// Optional arguments
+#[ivory_export]
+fn hello(input: Option<String>) {
+    printf(format!("Hello {}", other.unwrap_or("Rust".to_string())));
 }
 
 ivory_module!({