udpate readme and manifest

MANIFEST.md

@@ -1,16 +1,15 @@
+title: gr-foo
 brief: some utility blocks
+tags:
+  - foo
 author:
   - Bastian Bloessl <bloessl@ccs-labs.org>
 copyright_owner:
   - Bastian Bloessl
-dependencies:
-  - gnuradio (>= 3.7.4)
 repo: https://github.com/bastibl/gr-foo.git
-tags:
-  - foo
 website: https://github.com/bastibl/gr-foo
-title: gr-foo
 icon: http://www.ccs-labs.org/projects/wime/wime.png
+gr_supported_version: v3.7, v3.8, v3.9
 ---
 This is a collection of custom blocks that are not directly associated with a project. For sample applications see:
 

README.md

@@ -20,11 +20,10 @@ project. For sample applications see:
 
 ### Development
 
-Like GNU Radio, this module uses *master* and *maint* branches for development.
+Like GNU Radio, this module uses *maint* branches for development.
 These branches are supposed to be used with the corresponding GNU Radio
 branches. This means: the *maint-3.7* branch is compatible with GNU Radio 3.7,
-*maint-3.8* is compatible with GNU Radio 3.8, and *master* is compatible with
-GNU Radio master, which tracks the development towards GNU Radio 3.9.
+*maint-3.8* is compatible with GNU Radio 3.8, etc.