Update dependency mocha to v5.1.1 (dev)

This Merge Request updates dependency mocha from v5.0.5 to v5.1.1

Release Notes

v5.1.0

**🎉 Enhancements**

• #3210: Add --exclude option (@metalex9)

**🐛 Fixes**

• #3318: Fix failures in circular objects in JSON reporter (@jeversmann, [@boneskull])

**📖 Documentation**

• #3323: Publish actual API documentation! (@dfberry, [@Munter])
• #3299: Improve docs around exclusive tests (@nicgirault)

**🔩 Other**

• #3302, #3308, #3310, #3315, #3316: Build matrix improvements (more info) ([@outsideris], [@boneskull])
• #3272: Refactor reporter tests (@jMuzsik)

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v5.1.1

**🐛 Fixes**

• #3325: Revert change which broke --watch ([@boneskull])

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Commits

**v5.1.0**

• 2b5d04a add changes for v5.0.5 [ci skip]
• ffd760e Release v5.0.5
• 8e740c5 #1577 Add "--exclude" Option (#3210)
• 9ba8eca Refactor Reporter tests (#3272)
• d8522b4 remove 0-byte file [ci skip]
• 1701335 use exact version of minimatch [ci skip]
• 35dac3e use build stages for Travis CI (#3302)
• cd1c835 upgrade eslint; lint
• f2560e7 add update-contributors script; closes #3289 (#3290)
• ff9f3cf update stages and build matrices (#3308)
• 4ae26b2 improve caching performance in CI (#3310)
• 88b9882 update package-lock.json for v5.0.5 [ci skip]
• 7544bd3 further build improvements (#3315)
• d71b80a PATH workaround for Travis CI bug
• 8b6c957 optimize package-scripts.js
• 94e7289 doc precision for exclusive tests
• 8010501 fix wrong version in package.json! [ci skip]
• 741b0bd fix circular objects in json reporter; closes #2433 (#3318)
• 1acea30 Tap reporter: report thrown error messages (#3317)
• 2f48a23 Implement API documentation using npm:documantation.

**v5.1.1**

• 56e8452 update CHANGELOG for v5.1.0 [ci skip]
• 3ac8e55 Release v5.1.0
• 58efe58 update package-lock.json [ci skip]
• 2d1b49c fix ESLint problems and consolidate configuration
• 07e1ed2 update outdated info in docs/README.md [ci skip]

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This MR has been generated by Renovate Bot.