Options for assertion library, Mocha "interface"

[quartzmo]

The user needs to be able to override:

• Assertion librarby - default "chai", any string ok since user can implement own
• Mocha "interface" - default "bdd", any string ok since user can implement own

[sandstrom]

+1

[meleyal]

For the mean time this is also possible to set via JS, e.g.

window.assert = chai.assert
mocha.setup({ ui: 'bdd', globals: ['LiveReload'] })