Set dotStyle and activeDotStyle per mark

[ibash]

Fixes #206

This allows setting custom dot styling on a per mark basis. Tried to be as least-intrusive as possible, but let me know if you'd prefer a different approach.

[codecov-io]

Codecov Report

Merging #425 into master will decrease coverage by 0.2%. The diff coverage is 60%.

@@            Coverage Diff             @@
##           master     #425      +/-   ##
==========================================
- Coverage   83.47%   83.26%   -0.21%     
==========================================
  Files          10       10              
  Lines         478      484       +6     
  Branches      113      115       +2     
==========================================
+ Hits          399      403       +4     
- Misses         79       81       +2

Impacted Files	Coverage Δ
src/common/Steps.jsx	93.75% <60%> (-6.25%)	:arrow_down:
src/index.js	100% <0%> (ø)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update e7af5aa...99324fd. Read the comment docs.

[ibash]

cc @yesmeck what do you think?

[yoyo837]

Rebase please.

[regeter]

So sad that this simple PR never made it. I've been fighting for an hour trying to style a single dot.