Fix typos (#57)

Author: kianmeng

README.md

@@ -362,7 +362,7 @@ mocked-sessionmakers=database.WorkerSessionmaker database.SecondWorkerSessionmak
 
 ### <a name="writing-transactional-tests"></a>Writing transactional tests
 
-Once you have your [conftest file set up](#conftest-setup) and you've [overrided the
+Once you have your [conftest file set up](#conftest-setup) and you've [overridden the
 necessary connectables in your test configuration](#test-configuration), you're ready
 to write some transactional tests. Simply import one of the module's [transactional
 fixtures](#fixtures) in your test signature, and the test will be wrapped in a transaction.

tests/test_fixtures.py

@@ -83,7 +83,7 @@ def test_db_engine_changes_dont_persist(person, db_engine, db_session):
 def test_raise_programmingerror_rolls_back_transaction(db_testdir):
     '''
     Make sure that when a ProgrammingError gets raised and handled, the
-    connection will continue to be useable.
+    connection will continue to be usable.
     '''
     db_testdir.makepyfile("""
         import pytest