Sourcemap generation is slow

[schmod]

Ever since #103 was merged, source map generation is extremely slow (from ~2sec to 30+sec).

While I mostly understand the rationale behind #103, the current solution creates a fairly extreme performance bottleneck, especially when considering that Uglify can process the concatenated file (with sourcemaps enabled) in a fraction of the time.

Does mozilla/source-map really not a have a preferred/optimized way to do a simple concatenation?

There's a fast-sourcemap-concat module, although it seems to do a line-by-line concatenation, which might not address the issues that were fixed in #103.

[gonzoyumo]

Got it too :(

[bob-v-t]

Wow, since yesterday's release (1.0.0) the sourcemap generation is going a lot quicker. Thanks for your work on this!