Change navigation header

Author: odow

Diff for: _config.yml

@@ -111,12 +111,16 @@ css_inline: false # Will insert all styles into a single <style> block in the <h
 navigation_header:
 - title: Home
   url: /
-- title: Governance
-  url: /pages/governance
-- title: Code
-  url: /pages/code/
 - title: Documentation
   url: https://jump.dev/JuMP.jl/stable/
+- title: Community
+  items:
+  - title: Forum
+    url: https://discourse.julialang.org/c/domain/opt
+  - title: Chatroom
+    url: https://gitter.im/JuliaOpt/jump-dev
+  - title: Ecosystem
+    url: /pages/code/
 - title: Workshops
   items:
    - title: 2020
@@ -127,9 +131,9 @@ navigation_header:
      url: /meetings/bordeaux2018
    - title: 2017
      url: /meetings/mit2017
-- title: Forum
-  url: https://discourse.julialang.org/c/domain/opt
-- title: News
+- title: Governance
+  url: /pages/governance
+- title: Blog
   url: /pages/news/
 
 # TODO