Merge pull request #31 from nikomatsakis/structs-and-tuples

add a stucts-and-tuples chapter

Author: avadacatavra

reference/src/SUMMARY.md

@@ -14,5 +14,6 @@
   - [Unions](./active_discussion/unions.md)
   - [Uninitialized memory](./active_discussion/uninitialized_memory.md)
 - [Data representation](./representation.md)
+  - [Structs and tuples](./representation/structs-and-tuples.md)
 - [Optimizations](./optimizations.md)
   - [Optimizing immutable memory](./optimizations/immutable_memory.md) 

reference/src/representation.md

@@ -6,11 +6,6 @@
 
 https://github.com/rust-rfcs/unsafe-code-guidelines/issues/9
 
-## Representation of structs and tuples
-
-https://github.com/rust-rfcs/unsafe-code-guidelines/issues/11
-https://github.com/rust-rfcs/unsafe-code-guidelines/issues/12
-
 ## Representation of enums 
 
 https://github.com/rust-rfcs/unsafe-code-guidelines/issues/10