120 top level routing

[jameshadfield]

• Routing logic is in index.js - note that localhost:4000/flu redirects to nextflu
• To get the header to work in the main App I had to add some CSS (index.html) to remove sidebars and offset the Sidebar by the header height. Apparently there's an easier way How do I use sidebar with a fullwidth top header? balloob/react-sidebar#23 but I couldn't make it work. The drop-shadow doesn't go over the main bit, which is a bit rubbish.
• The titlebar / header is now inside About / Splash / App. Note that when you open the sidebar the titlebar changes...
• Issue make titlebar component responsive #122 is not addressed, so the titlebar isn't great on mobile
• About and splash pages done - help / methods etc not part of this PR
• I haven't looked into the image licenses
• I don't really know how to use flexbox, so it's a bit of a disaster when the width gets small

[trvrb]

I'm getting an error from Heroku when trying to push 120-top-level-routing that I'm not getting on master. This is:

remote:        > nextstrain-auspice@0.0.1 build:webpack /tmp/build_6057c9f69a4ad2029e973b314dfebf0b
remote:        > NODE_ENV=production webpack --config webpack.config.js
remote:        
remote:        fatal: Not a git repository (or any parent up to mount point /tmp)
remote:        Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
remote:        child_process.js:526
remote:        throw err;
remote:        ^
remote:        
remote:        Error: Command failed: git rev-parse --short HEAD
remote:        fatal: Not a git repository (or any parent up to mount point /tmp)
remote:        Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
remote:        
remote:        at checkExecSyncError (child_process.js:483:13)
remote:        at Object.execSync (child_process.js:523:13)
remote:        at Object.<anonymous> (/tmp/build_6057c9f69a4ad2029e973b314dfebf0b/webpack.config.js:5:4)
remote:        at Module._compile (module.js:570:32)
remote:        at Object.Module._extensions..js (module.js:579:10)
remote:        at Module.load (module.js:487:32)
remote:        at tryModuleLoad (module.js:446:12)
remote:        at Function.Module._load (module.js:438:3)
remote:        at Module.require (module.js:497:17)
remote:        at require (internal/module.js:20:19)

I'm investigating...

[trvrb]

This is killing Heroku: 4c6cc48#diff-11e9f7f953edc64ba14b0cc350ae7b9dR5. Heroku doesn't have a Git repo to run git rev-parse on. More info here: http://stackoverflow.com/questions/14583282/heroku-display-hash-of-current-commit