Wrote parsedown helper

- wrote unit tests to describe behavior of helper
  - created unit test bootstrap for module
- wrote helper class
- wrote factory for helper in Module class
- added Parsedown to dependencies for application
Replace LibraMarkdown with AgParsedown
Integrate parsedown into changelog

- s/markdown/parsedown/ in the view script
- fixed autoloading for AgParsedown module
CS fixes

- trailing whitespace
Merge branch 'feature/parsedown'

Use erusev/parsedown instead of LibraMarkdown for markdown parsing; gives us the
ability to use GitHub-flavored markdown for changelogs and documentation.