parsing of template issue: ${moment().toISOString()} does not work

i get this error after upgrading

aurelia-framework version "aurelia-framework": "^1.3.1",

the view-model code:
```
import moment from 'moment'

export class ComponentX {
constructor (router) {
this.router = router
this.moment = moment
}
```

then in view.html:
`${moment()}` -- works, return date as string
`${moment().toISOString()}` -- does not work. no method of moment can be called, it throws error:
`moment() is not a function`

when i downgrade to "aurelia-framework": "1.3.0" it works again.

Reproduce the template expression in view.html with aurelia-framework 1.3.1, comparing it with 1.3.0 and the shown view-model code. Trace how the binding parser handles moment() versus moment().toISOString(); done means method calls work again in the template without regressing the simpler expression.

Written by the indexing model from the issue text.