Added filename to top of .rs files

error_handling/errors1.rs

@@ -1,3 +1,4 @@
+// errors1.rs
 // This function refuses to generate text to be printed on a nametag if
 // you pass it an empty string. It'd be nicer if it explained what the problem
 // was, instead of just sometimes returning `None`. The 2nd test currently

error_handling/errors2.rs

@@ -1,3 +1,4 @@
+// errors2.rs
 // Say we're writing a game where you can buy items with tokens. All items cost
 // 5 tokens, and whenever you purchase items there is a processing fee of 1
 // token. A player of the game will type in how many items they want to buy,

error_handling/errors3.rs

@@ -1,3 +1,4 @@
+// errors3.rs
 // This is a program that is trying to use a completed version of the
 // `total_cost` function from the previous exercise. It's not working though--
 // we can't call the `try!` macro in the `main()` function! Why not?

error_handling/errorsn.rs

@@ -1,3 +1,4 @@
+// errorsn.rs
 // This is a bigger error exercise than the previous ones!
 // You can do it!
 //

error_handling/option1.rs

@@ -1,3 +1,4 @@
+// option1.rs
 // This example panics because the second time it calls `pop`, the `vec`
 // is empty, so `pop` returns `None`, and `unwrap` panics if it's called
 // on `None`. Handle this in a more graceful way than calling `unwrap`!

error_handling/result1.rs

@@ -1,3 +1,4 @@
+// result1.rs
 // Make this test pass! Scroll down for hints :)
 
 #[derive(PartialEq,Debug)]