Minor clean-up

Expand gitignore to include the usual py developing stuff, add an
__init__ to make this a legitimate package, move GPIO initialization
into the package init, import all stuff from input and output devices in
the package to enable the access demonstrated in the example, remove a
duplicate method from LightSensor, and make motion_detected a property
(for consistency with is_active which it presumably parallels).

.gitignore

@@ -1 +1,28 @@
-*.pyc
+*.py[cdo]
+
+# Editor detritus
+*.vim
+*.swp
+tags
+
+# Packaging detritus
+*.egg
+*.egg-info
+dist
+build
+eggs
+parts
+bin
+var
+sdist
+develop-eggs
+.installed.cfg
+
+# Installer logs
+pip-log.txt
+
+# Unit test / coverage reports
+coverage
+.coverage
+.tox
+