Allow user to configure chai options

[ahutchings]

Chai has three configurable options - http://chaijs.com/guide/styles/#configuration

It would be useful if karma-chai allowed the user to set these in the karma configuration.

[mikeabiezzi]

+1

[johngrogg]

You can possibly take a look at how karma-mocha does it. They look at the config.client.mocha for mocha configuration options. Seems you could use config.client.chai maybe?

[ehartford]

yes please! Need this

[ehartford]

This is fixed in #12
@xdissent just needs to merge it and release it