ToQuantity: Fix Decimal/Integer Overloads & add Ratio Overload

[cmoesel]

This PR contains fixes and enhancements to ToQuantity:

• Decimal and Integer overloads now properly set units to 1
• Ratio overload is now supported (divides ratio numerator by denominator)

Fixes #175

Submitter:

• [x] This pull request describes why these changes were made
• [x] Code diff has been done and been reviewed (it does not contain: additional white space, not applicable code changes, debug statements, etc.)
• [x] Tests are included and test edge cases
• [x] Tests have been run locally and pass
• [ ] Code coverage has not gone down and all code touched or added is covered.
• [x] Code passes lint and prettier (hint: use yarn run test:plus to run tests, lint, and prettier)
• [x] All dependent libraries are appropriately updated or have a corresponding PR related to this change
• [x] cql4browsers.js built with yarn run build:browserify if source changed.

Reviewer:

Name:

• [x] Code is maintainable and reusable, reuses existing code and infrastructure where appropriate, and accomplishes the task’s purpose
• [x] The tests appropriately test the new code, including edge cases
• [x] You have tried to break the code

[codecov-io]

Codecov Report

Merging #235 (f7b90f2) into master (ebaf5f9) will decrease coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #235      +/-   ##
==========================================
- Coverage   92.27%   92.26%   -0.02%     
==========================================
  Files          47       47              
  Lines        3975     3981       +6     
==========================================
+ Hits         3668     3673       +5     
- Misses        307      308       +1     

Impacted Files	Coverage Δ
src/elm/type.js	87.90% <100.00%> (+0.26%)	:arrow_up:
src/datatypes/quantity.js	87.50% <0.00%> (-1.05%)	:arrow_down:

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[cmoesel]

I was a bit perplexed how coverage went down, particularly in a file I did not modify. But it is because we used to call parseQuantity for all cases, which is clearly not the right thing to do. One of those cases (for numbers) set the units to '' in quantity.js -- but since that's not the behavior we want, we don't call that function that way anymore, so that line that sets units to '' is no longer covered. Honestly... I'm not worried about it -- but let me know if you are.