Terser syntax for exporting identifiers

[kristoferbaxter]

When exporting identifiers, we can avoid creating a variable reference to the name we want to export.

Also, we never currently inline export (even for sole export in a module) since we do not restore the name of the original export across the module.

[codecov-io]

Codecov Report

Merging #263 into master will increase coverage by 0.11%.
The diff coverage is 98.33%.

@@            Coverage Diff             @@
##           master     #263      +/-   ##
==========================================
+ Coverage   94.83%   94.94%   +0.11%     
==========================================
  Files          14       14              
  Lines        1432     1485      +53     
  Branches      142      151       +9     
==========================================
+ Hits         1358     1410      +52     
- Misses         70       71       +1     
  Partials        4        4

Impacted Files	Coverage Δ
src/transformers/exports.ts	94.79% <100%> (+0.4%)	⬆️
src/transformers/imports.ts	97.04% <96.77%> (-0.13%)	⬇️

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