Update mocha to version 2.5.2 🚀

[greenkeeperio-bot]

Hello :wave:

:rocket::rocket::rocket:

mocha just published its new version 2.5.2, 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 mocha – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

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The new version differs by 148 commits .

• fdbbe40 Release v2.5.2
• c094f20 Rebuild mocha.js
• 7c134ea Update CHANGELOG.md for v2.5.2 [ci skip]
• 25f9378 Add .envrc to .gitignore
• 49b5ff1 Avoid double and triple xUnit XML escaping (#2178)
• 015b809 Release v2.5.1
• 3ef083e update CHANGELOG.md [ci skip]
• bd9450b to-iso-string must be a dependency
• 30e917b Release v2.5.0
• 443697f rebuild mocha.js
• 9bfbc9e update CHANGELOG.md, contributors, .mailmap
• 524862b full browserification support; closes #880 (#2271)
• 9e8cbaa try different strategy for avoiding insecure sauce connect
• f8a3d86 trying to fix travis + sauce check for PRs and forks
• 0dde0fa don't run SauceLabs tests on PRs

There are 148 commits in total. See the full diff.

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