Make documentation mobile-friendly

More and more of our page views are coming from mobile devices (phones and tablets)¹; yet, the documentation only renders well on a desktop browser, and unreadable on a mobile device — the font is too small, and zooming in makes the page too large for the window, which means lots of scrolling around.

One way to fix this may be to use responsive CSS which would render content appropriately for an arbitrary screen size, whether the user is using a desktop/laptop, tablet, or phone.

Since more and more users are surfing and accessing information via mobile devices, it makes sense for us to fix it to make it easier to discover JanusGraph and learn about it.

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¹ This is a general trend, but I also have some statistics from my AdWords campaign that I'm running for JanusGraph, and 50+% of impressions and clicks are coming from mobile devices.

No documentation files or tests are named in the issue. Start by locating the documentation site's page and stylesheet entry points, then inspect the current layout on phone, tablet, and desktop widths. Done means documentation text is readable and fits arbitrary screen sizes without excessive zooming or horizontal scrolling.

Written by the indexing model from the issue text.