Fix weeks scale, plus other cleanup

- Weeks scale now gives more realistic view of week boundaries
- All week calculations now assume ISO weeks by default (options coming soon)
- Addresses bug part of #61
- Fixes #73
- Fixes #99
- Closes #112
- Closes #153
- Use `createPseudo` for custom jquery pseudo-selector definitions when available
- Other miscellaneous incremental code cleanup and refactoring.