use h1 tags to not render titles in sidebar

docs/administrator.md

-# Administrator Guide
+<h1>Administrator Guide</h1>
 
 Learn how to configure and manage the Postgres Operator in your Kubernetes (K8s)
 environment.

docs/developer.md

-# Developer Guide
+<h1>Developer Guide</h1>
 
 Read this guide if you want to debug the operator, fix bugs or contribute new
 features and tests.

docs/gsoc-2019/ideas.md

-
-# Google Summer of Code 2019
+<h1>Google Summer of Code 2019</h1>
 
 ## Applications steps
 

docs/index.md

-# Concepts
+<h1>Concepts</h1>
 
 The Postgres [operator](https://coreos.com/blog/introducing-operators.html)
 manages PostgreSQL clusters on Kubernetes (K8s):

docs/operator-ui.md

-# Postgres Operator UI
+<h1>Postgres Operator UI</h1>
 
 The Postgres Operator UI provides a graphical interface for a convenient
 database-as-a-service user experience. Once the operator is set up by database

docs/quickstart.md

-# Quickstart
+<h1>Quickstart</h1>
 
 This guide aims to give you a quick look and feel for using the Postgres
 Operator on a local Kubernetes environment.

docs/reference/cluster_manifest.md

-# Cluster manifest reference
+<h1>Cluster manifest reference</h1>
 
 Individual Postgres clusters are described by the Kubernetes *cluster manifest*
 that has the structure defined by the `postgresql` CRD (custom resource

docs/reference/command_line_and_environment.md

@@ -28,7 +28,7 @@ flags](https://godoc.org/github.com/golang/glog) are also supported. For
 instance, one may want to add `-alsologtostderr` and `-v=8` to debug the
 operator REST calls.
 
-## Environment variables
+# Environment variables
 
 The following environment variables are accepted by the operator:
 

docs/reference/operator_parameters.md

-# Configuration parameters
+<h1>Configuration parameters</h1>
 
 There are two mutually-exclusive methods to set the Postgres Operator
 configuration.

docs/user.md

-# User Guide
+<h1>User Guide</h1>
 
 Learn how to work with the Postgres Operator in a Kubernetes (K8s) environment.
 

manifests/postgres-operator.yaml

@@ -35,4 +35,3 @@ spec:
         # In order to use the CRD OperatorConfiguration instead, uncomment these lines and comment out the two lines above
         # - name: POSTGRES_OPERATOR_CONFIGURATION_OBJECT
         #  value: postgresql-operator-default-configuration
-          

mkdocs.yml

@@ -3,13 +3,14 @@ repo_url: https://github.com/zalando/postgres-operator
 theme: readthedocs
 
 nav:
-  - index.md
-  - quickstart.md
-  - operator-ui.md
-  - administrator.md
-  - user.md
-  - developer.md
+  - Concepts: 'index.md'
+  - Quickstart: 'quickstart.md'
+  - Postgres Operator UI: 'operator-ui.md'
+  - Admin guide: 'administrator.md'
+  - User guide: 'user.md'
+  - Developer guide: 'developer.md'
   - Reference:
-    - reference/operator_parameters.md
-    - reference/cluster_manifest.md
-    - reference/command_line_and_environment.md
+    - Config parameters: 'reference/operator_parameters.md'
+    - Manifest parameters: 'reference/cluster_manifest.md'
+    - CLI options and environment: 'reference/command_line_and_environment.md'
+  - Google Summer of Code 2019: 'gsoc-2019/ideas.md'