Support Theming

[lttb]

@iamstarkov @kof

There is some basic support for theming out of the box.

So do we need to use themed-functions for styled-jss?

TODO:

• [x] update docs about theming in styled-jss

[coveralls]

Coverage remained the same at 100.0% when pulling f1458d33f1a139cd516321326adc0289e7344d54 on feature/theming into ac3b05b42caa38758e45afaee9114be3df982525 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling f5f73c149e530f3b8fa0db61830ca1b3cca4e490 on feature/theming into ac3b05b42caa38758e45afaee9114be3df982525 on master.

[lttb]

@iamstarkov I need to refactor it with using theming function instead of props, so I hope I finish it this week

[coveralls]

Coverage decreased (-0.5%) to 99.524% when pulling de6235f24a2fbf21938620de87aeb7eb14d96b52 on feature/theming into 5adf8db68ba1caa3fe483e90685d4a7bcf85d61e on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 802f6205b830aaa03344837517aa0701f2e671de on feature/theming into 5adf8db68ba1caa3fe483e90685d4a7bcf85d61e on master.

[jmadson]

@kof What's needed before this can merge?

[kof]

We discussed to pass theme as a prop in order to stay consistent with cases where user can pass a theme over component prop, so we don't have a situation with 2 theme objects