Implement Redux, change username already taken error message

Description

• Refactored state management to use Redux
• Add user-facing error message for registering with a username already taken
• Update eslint-utils from 1.4.0 to 1.4.2

Fix deployment bugs and warnings

Description

• Update Procfile and project structure to deploy to Heroku properly
• Address compiler warnings
• Change website title to Data Runner

Initial Release

Description

• MVP for website completed
• User registration/login
• .gpx file uploading, parsing, and saving to database
• Activity stats, history, and heatmap widgets for a given user