options.urls not documented correctly

[Zach Gardner]

README.md shows the following:

mocha: {
test: {
urls: [ 'http://localhost:8888/example/test/test2.html' ],
},
},

This doesn't work as the task looks at options.
It should be:

mocha: {
test: {
options: {
urls: [ 'http://localhost:8888/example/test/test2.html' ],
}
}
}