Add support for label classes

[chirvo]

For being able to alter the looks of the label without depending on 'grid'.

[codecov]

Codecov Report

Merging #548 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #548   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files         162    162           
  Lines        1570   1570           
=====================================
  Hits         1570   1570

Impacted Files	Coverage Δ
packages/uniforms-bootstrap3/src/wrapField.js	100% <ø> (ø)	⬆️
packages/uniforms-bootstrap4/src/wrapField.js	100% <ø> (ø)	⬆️

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[radekmie]

Hi @bigchirv. Really small change looks good (docs!). Can you add it to the bootstrap3 theme too? A simple test would also be great.

[chirvo]

Thanks for pointing out writing the tests, really forgot about them. 😃

On what file should I add the documentation on the labelClassName prop for bootstrap 3/4?

[radekmie]

It should be in docs/api-fields.md.

[chirvo]

Okay, I added the entries in api-fields.md as suggested.

[radekmie]

Thank you @bigchirv!