You can use various markdown-previewer programs to see this documentation offline. Once you download No-CMS, you can find this documentation located at /doc/tutorial.md.
If you use chrome browser, you can install an extension named Markdown Preview. Once you install the extension, go to chrome://extensions and activate Allow access to file urls. Open up the documentation by using google chrome, and enjoy.
If you use firefox, you can install an addons named Markdown Viewer
You can also use github's atom text editor.