Enable --fast CLI flag for transpile mode only

[blakeembrey]

Related to #44.

Without --fast tests on typings-core:

npm run test-spec  7.98s user 0.52s system 72% cpu 11.691 total

With --fast tests on typings-core:

npm run test-spec  3.52s user 0.47s system 56% cpu 7.098 total

[coveralls]

Coverage decreased (-27.6%) to 60.262% when pulling 4f7df7c on fast-option into a1384b6 on master.

[coveralls]

Coverage decreased (-1.3%) to 86.638% when pulling 58d3e6b on fast-option into a1384b6 on master.

[mjohnsonengr]

1.5x is an understatement. Upgrading from 0.8 -> 0.9.1 got my test suite from 3.5 minutes to 22 seconds; the --fast flag then took me down to 2 seconds!

Awesome work and cheers @blakeembrey!! 😁

[blakeembrey]

Wow, that is ridiculous! Sorry it took so long for that improvement to make it's way in 😄

[mjohnsonengr]

Hah! No worries! I just now started working on getting our test suites to run in node last week and only hit the performance issues this morning before I found this upgrade! (previously it was a mess of hacks making them run with compiled JS coverage in the browser)