Customize nginx config to allow for pushstate

Summary: Adds custom nginx config to allow for pushstate urls

Test Plan:
Run `npm install`
Set `vm : true` in gulpfile.js
Run `gulp build`
Run `gulp docker`
Load the UI
Load "http://192.168.59.103:8080/posts/detail" directly to check it works

Reviewers: seth, eyedol, rjmackay

Reviewed By: rjmackay

Subscribers: dkobia

Maniphest Tasks: T605

Differential Revision: https://phabricator.ushahidi.com/D272