Merge pull request #210 from artiegold/master

Fix "it's".

docs/writing/structure.rst

@@ -251,7 +251,7 @@ Another way to say the same thing is to suggest using functions and procedures
 with as few implicit contexts and side-effects as possible. A function's
 implicit context is made up of any of the global variables or items in the persistence layer
 that are accessed from within the function. Side-effects are the changes that a function makes
-to it's implicit context. If a function saves or deletes data in a global variable or
+to its implicit context. If a function saves or deletes data in a global variable or
 in the persistence layer, it is said to have a side-effect.
 
 Carefully isolating functions with context and side-effects from functions with