Add predicates for string

[sh0hei]

• ValidByte
• ValidShort
• ValidFloat

[codecov]

Codecov Report

Merging #492 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #492      +/-   ##
==========================================
+ Coverage   94.31%   94.33%   +0.02%     
==========================================
  Files          62       62              
  Lines         668      671       +3     
  Branches       13       13              
==========================================
+ Hits          630      633       +3     
  Misses         38       38

Impacted Files	Coverage Δ
...red/src/main/scala/eu/timepit/refined/string.scala	100% <100%> (ø)	⬆️

---

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 38c9297...73f8a75. Read the comment docs.

[fthomas]

This LGTM, thanks @sh0hei!
Could you do me a favor and add this change to the release notes (notes/0.9.1.markdown)?

[sh0hei]

Sorry I did not notice.
added to notes/0.9.1.markdown 👍

[fthomas]

Thanks!