Fix an issue with aliasing apiclient submodules.

The aliasing of `googleapiclient` as `apiclient` doesn't play nicely with
imports of the form `from apiclient import foo`. This is far from the most
elegant fix, but it gets the job done.
diff --git a/apiclient/__init__.py b/apiclient/__init__.py
index 5db22a1..5efb142 100644
--- a/apiclient/__init__.py
+++ b/apiclient/__init__.py
@@ -23,3 +23,18 @@
 from googleapiclient import schema
 
 __version__ = googleapiclient.__version__
+
+_SUBMODULES = {
+    'channel': channel,
+    'discovery': discovery,
+    'errors': errors,
+    'http': http,
+    'mimeparse': mimeparse,
+    'model': model,
+    'sample_tools': sample_tools,
+    'schema': schema,
+}
+
+import sys
+for module_name, module in _SUBMODULES.iteritems():
+  sys.modules['apiclient.%s' % module_name] = module