Corrected some typos in documentation.

docs/topics/performance.txt

@@ -86,7 +86,7 @@ Get things right from the start
 -------------------------------
 
 Some work in optimization involves tackling performance shortcomings, but some
-of the work can be built in to what you'd do anyway, as part of the good
+of the work can be built-in to what you'd do anyway, as part of the good
 practices you should adopt even before you start thinking about improving
 performance.
 

docs/topics/testing/index.txt

@@ -21,7 +21,7 @@ inspect your application's output and generally verify your code is doing what
 it should be doing.
 
 The preferred way to write tests in Django is using the :mod:`unittest` module
-built in to the Python standard library. This is covered in detail in the
+built-in to the Python standard library. This is covered in detail in the
 :doc:`overview` document.
 
 You can also use any *other* Python test framework; Django provides an API and