Patched [Button] styles and props and remove child docs

[hyochan]

Description

More concise and robust implementation on [Button]. Previously, the [Button] had some dirty props in styling. Especially, the root and the button style props confused many users on their actual purposes. I've managed to remove them simplified into one container style.

Button also had a default width and height, which made it difficult to override the height from the parent given in flex UI (alignSelf: stretch). It now automatically calculates the children and generates width and height automatically. This can also set manually.

• Released to 0.0.26.
• Remove all the underlined readmes because we now have the storybook.
• Organize readmes and folder structures.

Related Issues

350

Checklist

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• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] Run yarn test or yarn test -u if you need to update snapshot.
• [x] Run yarn lint
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[codecov[bot]]

Codecov Report

Merging #369 (69b23f3) into master (2335d51) will decrease coverage by 0.23%. The diff coverage is 70.00%.

@@            Coverage Diff             @@
##           master     #369      +/-   ##
==========================================
- Coverage   82.03%   81.80%   -0.24%     
==========================================
  Files          36       35       -1     
  Lines        1108     1110       +2     
  Branches      357      359       +2     
==========================================
- Hits          909      908       -1     
- Misses         90       91       +1     
- Partials      109      111       +2