add usage docs

Author: schworer

docs/usage.rst

@@ -0,0 +1,39 @@
+Usage
+=====
+
+Here is some basic usage information::
+
+    import zencoder
+    zen = zencoder.Zencoder()
+    zen.jobs.list()
+
+        from zencoder import Zencoder
+        zen = Zencoder('abc123') # enter your api key
+
+        # creates an encoding job with the defaults
+        job = zen.job.create('http://input-file/movie.avi')
+        print job.code
+        print job.body
+        print job.body['id']
+
+        # get the transcode progress of the first output
+        progress = zen.output.progress(job.body['outputs'][0]['id'])
+        print progress.body
+
+
+        # configure your outputs with dictionaries
+        iphone = {
+                     'label': 'iPhone',
+                     'url': 's3://output-bucket/output-file-1.mp4',
+                     'width': 480,
+                     'height': 320
+                 }
+        web = {
+                  'label': 'web',
+                  'url': 's3://output-bucket/output-file.vp8',
+                  'video_codec':, 'vp8'
+              }
+        # the outputs kwarg requires an iterable
+        outputs = (iphone, web)
+        another_job = zen.job.create(input_url, outputs=outputs)
+