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.

[lahmatiy]

CSSO itself doesn't use source-map directly (only as dev dependency for tests). Update should be in css-tree or/and csso-cli (so you need to fill an issue in that repos). Now they're using 6.x branch, because 0.7+ is using async API for SourceMapCustomer that's not suitable. Moreover, any performance boost is gained only in case when you input and output have source maps and huge enough – so that's not an issue in many cases.