Line numbers don't respect sourcemaps

[garybernhardt]

When running teenytest file.js:10, the "10" should refer to the line number in whatever the original source was. If it's been compiled from TypeScript etc., that line number will be different. Teenytest should use source maps to trace back to the original line.

Likewise for exceptions; they point to line numbers in the built code, not the original source.

[searls]

Cross-linking discussion in: testdouble/function-names-at-line#1