Minor documentation cleanups

src/escape.rs

@@ -16,9 +16,9 @@ pub struct EscapePass;
 
 /// **What it does:** This lint checks for usage of `Box<T>` where an unboxed `T` would work fine. It is `Warn` by default.
 ///
-/// **Why is this bad?** This is an unnecessary allocation, and bad for performance
+/// **Why is this bad?** This is an unnecessary allocation, and bad for performance. It is only necessary to allocate if you wish to move the box into something.
 ///
-/// It is only necessary to allocate if you wish to move the box into something.
+/// **Known problems:** None
 ///
 /// **Example:**
 ///

src/precedence.rs

@@ -4,7 +4,7 @@ use syntax::ast::*;
 
 use utils::{span_lint, snippet};
 
-/// **What it does:** This lint checks for operations where precedence may be unclear and `Warn`'s about them by default, suggesting to add parentheses. Currently it catches the following:
+/// **What it does:** This lint checks for operations where precedence may be unclear and `Warn`s about them by default, suggesting to add parentheses. Currently it catches the following:
 /// * mixed usage of arithmetic and bit shifting/combining operators without parentheses
 /// * a "negative" numeric literal (which is really a unary `-` followed by a numeric literal) followed by a method call
 ///