Passing $parent to value converter and adding a binding behavior offends the parser.

[CuddleBunny]

I'm submitting a bug report

• Library Version:
  1.2.0

Please tell us about your environment:

• Operating System:
  Windows 10

• Node Version:
  8.1.0

• NPM Version:
  5.0.3

• JSPM OR Webpack AND Version
  JSPM 0.16.53

• Browser:
  all
• Language:
  all

Current behavior:
When passing $parent to a value converter and then using a binding behavior I get an Error: Unexpected character &.

Sample:
https://gist.run/?id=4e78f4b92109035f346caf2ca6153408

Strangely enough, if I wrap it in object notation like so: { vm: $parent } and pass that, it works just fine. This only seems to affect $parent and not $this. I've not tested any of the other contextual properties.

Expected/desired behavior:

• What is the expected behavior?
  Expression will parse without error, and behave like the workaround.