1.7.4 Release

- Adds source map to compiled output
- Removes legacy `demo.html`
- Drops IE<9 support
- Updates License and Copyright
- Changes compat to be lazy-loaded and memoized. Closes #98. Fixes #91
- Fixes formatting in test files
- Adds `thumbColor` option, to allow user-defined thumb colors. Closes #102
- Adds, and removes, a DOM body if required for testing. Closes #93