Add titles to doc pages.

doc/api/deploy_keys.md

-## Deploy Keys
+# Deploy Keys
 ### List deploy keys

doc/api/groups.md

+# Groups
+
 ## List project groups
 Get a list of groups. (As user: my groups, as admin: all groups)

doc/api/issues.md

+# Issues
+
 ## List issues
 Get all issues created by authenticated user. This function takes pagination parameters

doc/api/merge_requests.md

+# Merge requests
+
 ## List merge requests
 Get all merge requests for this project.

doc/api/milestones.md

+# Milestones
+
 ## List project milestones
 Returns a list of project milestones.

doc/api/notes.md

+# Notes
+
 Notes can be wall notes or comments on snippets, issues or merge requests.
 ## Wall

doc/api/project_snippets.md

+# Project snippets
+
 ## List snippets
 Get a list of project snippets.

doc/api/projects.md

-## Projects
+# Projects
 ### List projects

doc/api/repositories.md

+# Repositories
+
 ## List project repository tags
 Get a list of repository tags from a project, sorted by name in reverse alphabetical order.

doc/api/repository_files.md

-# CRUD for repository files
+# Repository files
+
+## CRUD for repository files
 ## Create, read, update and delete repository files using this API

doc/api/session.md

+# Session
+
 Login to get private token
 ```

doc/api/system_hooks.md

+# System hooks
+
 All methods require admin authorization.
 The url endpoint of the system hooks can be configured in [the admin area under hooks](/admin/hooks).

doc/api/users.md

+# Users
+
 ## List users
 Get a list of users.

doc/install/database_mysql.md

+# Database Mysql
+
 ## Note
 We do not recommend using MySQL due to various issues. For example, case [(in)sensitivity](https://dev.mysql.com/doc/refman/5.0/en/case-sensitivity.html) and [problems](http://bugs.mysql.com/bug.php?id=65830) that [suggested](http://bugs.mysql.com/bug.php?id=50909) [fixes](http://bugs.mysql.com/bug.php?id=65830) [have](http://bugs.mysql.com/bug.php?id=63164).

doc/install/installation.md

+# Installation
+
 # Select Version to Install
 Make sure you view [this installation guide](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/install/installation.md) from the branch (version) of GitLab you would like to install. In most cases
 this should be the highest numbered stable branch (example shown below).

doc/install/requirements.md

-# Operating Systems
+# Requirements
+
+## Operating Systems
 GitLab is developed for the Linux operating system. For the installations options and instructions please see [the installation section of the readme](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/README.md#installation).

doc/legal/corporate_contributor_license_agreement.md

+# Corporate contributor license agreement
+
 You accept and agree to the following terms and conditions for Your present and future Contributions submitted to GitLab B.V.. Except for the license granted herein to GitLab B.V. and recipients of software distributed by GitLab B.V., You reserve all right, title, and interest in and to Your Contributions.
 1. Definitions.

doc/legal/individual_contributor_license_agreement.md

+# Individual contributor license agreement
+
 You accept and agree to the following terms and conditions for Your present and future Contributions submitted to GitLab B.V.. Except for the license granted herein to GitLab B.V. and recipients of software distributed by GitLab B.V., You reserve all right, title, and interest in and to Your Contributions.
 1. Definitions.

doc/markdown/markdown.md

+# Markdown
+
 ----------------------------------------------
 Table of Contents

doc/permissions/permissions.md

+# Permissions
+
 Users have different abilities depending on the access level they have in a particular group or project.
 If a user is both in a project group and in the project itself, the highest permission level is used.
 If a user is a GitLab administrator they receive all permissions.