Move documentation to gh-pages

The documentation is out of date. Many references to refactored classes still exist and it leads one to question what else may not be accurate. Consider moving the documentation from a Wiki to the gh-pages branch. This has many benefits including:

• gh-pages can be managed at the same time as the source code itself.
• gh-pages can go through the same pull request process for review prior to integration.
• gh-pages uses simple Markdown and can benefit from Jekyll templating to produce a more USGS visually-compliant product.
• gh-pages can be updated as part of an integration hook to keep it up-to-date with the code itself.