Remove gzip references in Assets plugin README

gzip filter removed in:
https://github.com/miracle2k/webassets/commit/d0fb2414208353625ee04cf236e6961efdff8f59

Fixes #115

assets/Readme.rst

@@ -13,7 +13,7 @@ functions, including:
 * CSS compiler (``less``, ``sass``, ...)
 * JS minifier (``uglifyjs``, ``yui_js``, ``closure``, ...)
 
-Others filters include gzip compression, integration of images in CSS via data
+Others filters include CSS URL rewriting, integration of images in CSS via data
 URIs, and more. Webassets can also append a version identifier to your asset
 URL to convince browsers to download new versions of your assets when you use
 far-future expires headers. Please refer to the `Webassets documentation`_ for
@@ -51,11 +51,11 @@ Another example for Javascript:
 
 .. code-block:: jinja
 
-    {% assets filters="uglifyjs,gzip", output="js/packed.js", "js/jquery.js", "js/base.js", "js/widgets.js" %}
+    {% assets filters="uglifyjs", output="js/packed.js", "js/jquery.js", "js/base.js", "js/widgets.js" %}
         <script src="{{ SITEURL }}/{{ ASSET_URL }}"></script>
     {% endassets %}
 
-The above will produce a minified and gzipped JS file:
+The above will produce a minified JS file:
 
 .. code-block:: html