Please upgrade source-map to 0.7.2 to get speed improvements

[andreicristianpetcu]

The latest source-map which is v0.7.2 got support for WebAssembly and it is 10 times faster than the old one. More info here:

https://github.com/mozilla/source-map/blob/master/CHANGELOG.md#072
http://fitzgeraldnick.com/2018/02/26/speed-without-wizardry.html
https://hacks.mozilla.org/2018/01/oxidizing-source-maps-with-rust-and-webassembly/
firefox-devtools/debugger#5598

Please update so you would get 10 times speed improvements for your library in Firefox, 9 times in Safari and 5 times in Chrome.

[jonschlinkert]

it's in the pipeline, thanks

[danez]

Only problem with this is that source-map dropped support for node <8 in this version.

[jonschlinkert]

I'd like to externalize source maps completely. Perhaps instead of options.sourcemap being a boolean, we can allow the user to pass a function - which could be snapdragon-sourcemaps or a custom function.

Thoughts?