Update uglify-js to the latest version 🚀

[greenkeeper]

Version 2.8.0 of uglify-js just got published.

Dependency	uglify-js
Current Version	2.7.5
Type	devDependency

The version 2.8.0 is not covered by your current version range.

Without accepting this pull request your project will work just like it did before. There might be a bunch of new features, fixes and perf improvements that the maintainers worked on for you though.

I recommend you look into these changes and try to get onto the latest version of uglify-js.
Given that you have a decent test suite, a passing build is a strong indicator that you can take advantage of these changes by merging the proposed change into your project. Otherwise this branch is a great starting point for you to work on the update.

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Commits

The new version differs by 48 commits .

• 0b0296e v2.8.0
• 872270b improve error messages (#1506)
• b1c593a add harmony branch details in README (#1507)
• 13be50a faster tree transversal (#1462)
• 16cd5d5 consolidate evaluate & reduce_vars (#1505)
• 834f9f3 update docs for pure_funcs & drop_console (#1503)
• cf0951f allow --in-source-map inline (#1490)
• 852f784 Avoid using exports when undefined (#1471)
• 229e42c Merge pull request #1485 from alexlamsl/merge-2.8.0
• 4e49302 enable collapse_vars & reduce_vars by default
• 1e51586 Support marking a call as pure
• d48a308 Fix: AST_Accessor missing start / end tokens
• 26fbeec fix pure_funcs & improve side_effects
• 8898b8a clean up max_line_len
• ec64acd introduce unsafe_proto

There are 48 commits in total. See the full diff.

Not sure how things should work exactly?

There is a collection of frequently asked questions and of course you may always ask my humans.

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Your Greenkeeper Bot 🌴

[CLAassistant]

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