Add comment in README linking to UAX #11 for further details.

Author: theindigamer

README.md

@@ -1,8 +1,9 @@
 # unicode-width
 
 Determine displayed width of `char` and `str` types according to
-[Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/)
-rules.
+[Unicode Standard Annex #11][UAX11] rules.
+
+[UAX11]: (http://www.unicode.org/reports/tr11/)
 
 [![Build Status](https://travis-ci.org/unicode-rs/unicode-width.svg)](https://travis-ci.org/unicode-rs/unicode-width)
 
@@ -28,11 +29,19 @@ width. For example, the woman scientist emoji comprises of a woman emoji, a
 zero-width joiner and a microscope emoji.
 
 ```rust
+extern crate unicode_width;
+use unicode_width::UnicodeWidthStr;
+
+fn main() {
     assert_eq!(UnicodeWidthStr::width("👩"), 2); // Woman
     assert_eq!(UnicodeWidthStr::width("🔬"), 2); // Microscope
     assert_eq!(UnicodeWidthStr::width("👩‍🔬"), 4); // Woman scientist
+}
 ```
 
+See [Unicode Standard Annex #11](UAX11) for precise details on what is and isn't
+covered by this crate.
+
 ## features
 
 unicode-width does not depend on libstd, so it can be used in crates