Refactor OrderBookSnapshot and date utils

[alvyn279]

Refactor the app's OrderBookSnapshot component. The functionality depends too much on component states.

Tasks

• [x] Migrate globals from component state variables to redux variables
• [x] Partition render() into multiple functions
• [x] Clean up date-utils functions
  • [x] Remove redundant functions
  • [x] Rename functions
• [x] Fix tests
• [ ] ~Improve testing coverage in date-utils~

Overall, also look for improvements on lifecycle management.