Add showPassedTests config parameter

[lube]

Just a little fork, I really don't if this is works for anyone else, but I felt it was necessary when you had a ton of tests.

Will add docs and test if accepted.

usage:
mochaReporter: {
...
showPassedTests: false, //default true
...
}

[4kochi]

Thanks for the pull request. Sounds reasonable. Will have a look after my vacation.

[lube]

Thanks, enjoy your vacation!

[4kochi]

Hey @lube, looks fine for me. Can you add some documentation in the readme within this pull request. Then I will be able to merge it. Thanks.

[4kochi]

Ping @lube