Document expression order for tuple expressions.

Also removes a "you", alphabetizes the link refs, links to the
disambiguated parenthetical expression, and moves a link to a link
ref.

I probably should have made multiple commits. Sorry.

src/expressions/tuple-expr.md

@@ -10,17 +10,29 @@
 > &nbsp;&nbsp; ( [_Expression_] `,` )<sup>+</sup> [_Expression_]<sup>?</sup>
 
 Tuples are written by enclosing zero or more comma-separated expressions in
-parentheses. They are used to create [tuple-typed](../types/tuple.md)
-values.
+parentheses. They are used to create [tuple-typed] values.
 
 ```rust
 (0.0, 4.5);
 ("a", 4usize, true);
 ();
 ```
 
-You can disambiguate a single-element tuple from a value in parentheses with a
-comma:
+The inner expressions are evaluated from left to right.
+
+```rust
+# // Using vec instead of array to avoid references
+# // since there is no stable owned array iterator
+# // at the time this example was written.
+let mut one_two = vec![1, 2].into_iter();
+assert_eq!(
+    (1, 2),
+    (one_two.next().unwrap(), one_two.next().unwrap())
+);
+```
+
+Single-element tuples are disambiguated from a [parenthetical expression] with a
+comma before the closing parethesis:
 
 ```rust
 (0,); // single-element tuple
@@ -54,8 +66,10 @@ let unit_x = Point(1.0, 0.0);
 assert_eq!(unit_x.0, 1.0);
 ```
 
-[Inner attributes]: ../attributes.md
-[TUPLE_INDEX]: ../tokens.md#tuple-index
 [_Expression_]: ../expressions.md
 [_InnerAttribute_]: ../attributes.md
 [attributes on block expressions]: block-expr.md#attributes-on-block-expressions
+[Inner attributes]: ../attributes.md
+[parenthetical expression]: grouped-expr.md
+[tuple-typed]: ../types/tuple.md
+[TUPLE_INDEX]: ../tokens.md#tuple-index