Prepared documentation for publication

[weierophinney]

• Checked for tables (none) (Fixes #16)
• Checked and corrected all headers (Fixes #13)
• Checked and corrected all code blocks (Fixes #14)
• Checked and corrected all blockquotes (Fixes #17)
• Edited for content and markup (Fixes #15)
• Converted to mkdocs
• Added landing page

Additionally, added documentation build automation via Travis-CI; preview is at https://zendframework.github.io/zend-config/

[gianarb]

:+1: Thanks