Update gulp-uglify to version 1.5.0 🚀

[greenkeeperio-bot]

Hello 👋

🚀🚀🚀

gulp-uglify just published its new version 1.5.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of gulp-uglify – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging 🌴

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The new version differs by 12 commits .

• e9fe539 1.5.0
• 0555181 Fix the case where the generated source maps contains a null source content
• 289a910 Merge pull request #147 from terinjokes/greenkeeper-uglify-js-2.6.0
• 1814403 chore(package): update uglify-js to version 2.6.0
• e3709af fix(createError): separate createError into own module
• 735e04d chore(format): use a consistent format
• 03c672a Merge pull request #140 from terinjokes/greenkeeper-istanbul-0.4.0
• 1a1325d chore(CI): add AppVeyor configuration
• b4e8e53 chore(package): update istanbul to version 0.4.0
• b646e2a Merge pull request #139 from terinjokes/greenkeeper-istanbul-0.3.22
• 5e00139 chore(CI): upload to coveralls in after_success
• 36bf554 chore(package): update istanbul to version 0.3.22

See the full diff.

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