Bump mocha from 1.7.0 to 1.8.0

Bumps [mocha](https://github.com/freerange/mocha) from 1.7.0 to 1.8.0.
- [Release notes](https://github.com/freerange/mocha/releases)
- [Changelog](https://github.com/freerange/mocha/blob/master/RELEASE.md)
- [Commits](freerange/mocha@v1.7.0...v1.8.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile.lock

@@ -184,7 +184,7 @@ GEM
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
-    mocha (1.7.0)
+    mocha (1.8.0)
       metaclass (~> 0.0.1)
     money (6.13.1)
       i18n (>= 0.6.4, <= 2)