(#175) Update changelog.md

Added the missing information that was added in the releases section, and not here.
(#175) Corrected unordered list

Added in the * to make an unordered list
(#174) Added original Markdown files back in

- Due to issues after StyleCop and FxCop'ing the Markdown.cs and TextToFlowDocumentConverter.cs files, adding originals back in
- Have marked them as auto-generated and GeneratedCode so that both StyleCop and FxCop ignore them
Merge pull request #178 from gep13/feature/Issue-174

Added original Markdown files back in
(#81) Started creating an about page

- Based on the about page in Github for Windows
- Planning on includes the release notes that are already stored in source control
- Use Markdown to render contents of file

Todo:
- Include list of thank you's, i.e. RayGun
- Might also want to include references to all other 3rd Party tools, i.e. Mahapps, etc.
(#81) More changes to include About Information

- Added helper method to extract text from Embedded Resources
- Removed hardcoded Release Notes that was there for testing
- Created placeholder for About information page