Combine jimi-c and bcoca's ideas and work on hooking module-utils into PluginLoader.

This version just gets the relevant paths from PluginLoader and then
uses the existing imp.find_plugin() calls in the AnsiballZ code to load
the proper module_utils.

Modify PluginLoader to optionally omit subdirectories (module_utils
needs to operate on top level dirs, not on subdirs because it has
a hierarchical namespace whereas all other plugins use a flat
namespace).

Rename snippet* variables to module_utils*

Add a small number of unittests for recursive_finder

Add a larger number of integration tests to demonstrate that
module_utils is working.

Whitelist module-style shebang in test target library dirs

Prefix module_data variable with b_ to be clear that it holds bytes data

test/integration/targets/module_utils/library/test_failure.py

@@ -0,0 +1,14 @@
+#!/usr/bin/python
+
+results = {}
+# Test that we are rooted correctly
+# Following files:
+#   module_utils/yak/zebra/foo.py
+try:
+    from ansible.module_utils.zebra import foo
+    results['zebra'] = foo.data
+except ImportError:
+    results['zebra'] = 'Failed in module as expected but incorrectly did not fail in AnsiballZ construction'
+
+from ansible.module_utils.basic import AnsibleModule
+AnsibleModule(argument_spec=dict()).exit_json(**results)