Update styles to reflect changes in new Material Design guidelines

Google just unveiled the next stage for [Material Design](https://material.io/) and updated its stylistic guidelines. Some of the changes may require changes to `daemonite-material` in order to stay up to date. These changes will be listed here as a ship list for a future release (probably v4.2).

New Material [guidelines](https://material.io/design/guidelines-overview/) vs previous [guidelines](https://material.io/archive/guidelines/).

# General changes
- [x] Increase default border radius from `2px` to `4px`
- [ ] New overlay specs
- [x] Update default colours
- [ ] Update typography

# Individual component changes
- [ ] Check new specs for the following components:
- [ ] App bars (`.navbar`)
- [ ] Buttons (`.btn`)
- [ ] Cards (`.card`)
- [ ] Chips (`.chip`)
- [ ] Data tables (`.table`)
- [ ] Dialogs (`.modal`)
- [ ] Lists (`.list-group` and `.expansion-panel`)
- [ ] Menus (`.dropdown-menu` and `.menu`)
- [ ] Navigation drawers (`.navdrawer`)
- [ ] Progress indicators (`.progress`)
- [ ] Selection controls (`.custom-control`)
- [ ] Sliders (`.custom-range`)
- [ ] Snackbars (`.snackbar`)
- [ ] Tabs (`.nav-tabs`)
- [ ] Text fields (`.form-control`)
- [ ] Tooltips (`.tooltip`)

## App bars (bottom and top)
- [ ] Dense app bar
- [ ] Extended app bar
- [ ] Is [inset FAB](https://material.io/design/assets/1xkb-3HQEAsb0IA292GLCziMMh6QE1YIX/anatomy-fab-cut.png) easy to implement?

## Banners
- [ ] New component (banner probably can translate to Bootstrap's `.jumbotron`)

## Buttons
- [ ] Outlined button

## Buttons: floating action button
- [ ] Extended FAB

## Chips
- [ ] Outlined chip
- [ ] States (i.e. `.chip-danger`, `.chip-success`, `.chip-warning`, etc.)

## Dialogs
- [ ] Scrolling dialog

## Navigation drawers
- [ ] Bottom drawer

## Progress indicators
- [ ] Determinate circular progress indicator

## Text fields
- [ ] Outlined text field

**This list is not complete yet.**