Changed a few words

I changed was build > was built and reorganized a few sentences to be more clear.

docker/models/images.py

@@ -188,10 +188,10 @@ def build(self, **kwargs):
         Build an image and return it. Similar to the ``docker build``
         command. Either ``path`` or ``fileobj`` must be set.
 
-        If you have a tar file for the Docker build context (including a
-        Dockerfile) already, pass a readable file-like object to ``fileobj``
-        and also pass ``custom_context=True``. If the stream is compressed
-        also, set ``encoding`` to the correct value (e.g ``gzip``).
+        If you already have a tar file for the Docker build context (including a
+        Dockerfile), pass a readable file-like object to ``fileobj``
+        and also pass ``custom_context=True``. If the stream is also compressed,
+        set ``encoding`` to the correct value (e.g ``gzip``).
 
         If you want to get the raw output of the build, use the
         :py:meth:`~docker.api.build.BuildApiMixin.build` method in the
@@ -244,7 +244,7 @@ def build(self, **kwargs):
 
         Returns:
             (tuple): The first item is the :py:class:`Image` object for the
-                image that was build. The second item is a generator of the
+                image that was built. The second item is a generator of the
                 build logs as JSON-decoded objects.
 
         Raises: