Additional patterns so espower can be used with the new `t.try()` assertion

[Mark Wubben]

avajs/ava#1947 landed a new t.try() assertion. It's experimental, one of the reasons for which is that this preset doesn't recognize it yet.

We need to allow additional patterns for espower, depending on the outcome of this issue on our ESLint plugin: avajs/eslint-plugin-ava#273.