Mobile nav enhancement

[taramk]

• top nav should be moved to a fixed bottom bar

SIDEBAR

• sidebar should open on top of main panel, not push the main panel to the side
• tapping the "sidebar" icon toggles the sidebar drawer open and closed
• tapping a nav item in the sidebar will close the sidebar and redirect the user to the specified node
• sidebar drawer will scroll if necessary

SEARCH

• search opens up in a modal with a translucent overlay
• search interactions should work similar to sidebar interactions - tap a search result item to navigate to it or tap the search icon in the bottom bar to close search.

style updates (tara can do these later)

• sidebar drawer has an increased font size and padding for bigger tap targets
• search bar will also need a larger font size and tap targets

prototype:
https://www.figma.com/file/bGzEZo0NYHhWGJO95kwF3p/Treehouse-App?node-id=207%3A2585&t=WN6qaMSfuAkDsCyJ-1

[taramk]

assigning to myself so i can add mockups

[taramk]

@progrium will break down the implementation details, maybe split up into separate tickets

[progrium]

[deleted]

[progrium]

Pushed preliminary implementation. Most minor things can be fixed with css (sizing), but noticing more thought needs to be put into multiple panels, etc.