Fix missing/incorrect form-* classes for checkbox() and select().

[ndm2]

fixes #369

[codecov]

Codecov Report

Merging #373 (1be2f9e) into master (6924ce4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #373   +/-   ##
=========================================
  Coverage     99.23%   99.23%           
- Complexity      368      369    +1     
=========================================
  Files            21       21           
  Lines          1043     1046    +3     
=========================================
+ Hits           1035     1038    +3     
  Misses            8        8           

Impacted Files	Coverage Δ
src/View/Helper/FormHelper.php	99.13% <100.00%> (+<0.01%)	⬆️

---

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 6924ce4...1be2f9e. Read the comment docs.