Improve Collapsible component

[meenahoda]

• collapsible to user builder rather than constructing string template
• add tooltip
• add spacing
• ability to control open/close with model

[codecov]

Codecov Report

Merging #268 (319f7f7) into master (b989131) will decrease coverage by 0.14%.
The diff coverage is 10.71%.

@@            Coverage Diff             @@
##           master     #268      +/-   ##
==========================================
- Coverage   33.70%   33.56%   -0.15%     
==========================================
  Files          75       75              
  Lines        2148     2166      +18     
==========================================
+ Hits          724      727       +3     
- Misses       1424     1439      +15     

Impacted Files	Coverage Δ
lib/builders/Collapsible.js	12.50% <10.71%> (+3.40%)	⬆️

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