New content for getting started, about, and nav menu

[jessmc]

In this pull request:

• Created the page Getting Started with some content and youtube video 'Welcome to TaxBrain'
• Added youtube video 'Welcome to Open Source Policy Center' to about page between 'Our Mission' and 'Our History'
• Made link changes to the navigation menu in the header

Thank you!

[MattHJensen]

Thanks for this one, too. Also early next week for feedback.

[hdoupe]

@jessmc We moved all of the flatblock contents from the django admin portion of the site into the repo. It looks like there is a small merge conflict. I tried to resolve it but it doesn't look like that changed anything. Would you mind taking a look at this before I break something?

Otherwise, this looks great. We are pushing a new version of PolicyBrain to the test server today. So, if you could resolve this by 3 or 4 PM EST that would be great. If not, I should be able to resolve the conflict.

cc @MattHJensen @mikejpratt

[jessmc]

Hi @hdoupe ! I just took a look and think I was able to resolve the conflict. Please let me know if this helps, and if you need anything else from me!
Thanks,
Jessica

[hdoupe]

@jessmc Looks great. Thanks for the quick response!