Improving error recovery

[doorgan]

Following discussion in #65

One thing that caught my attention is that we have a test with this snippet(doesn't drop the cursor node):

%{state |
          foo: s
        __cursor__()
        ,
          bar: Foo.Bar.load(state.foo, state.baz)}

This would incorrectly report an unexpected ) for the Foo.Bar.load call before the fix in #65, but then I noticed that after parsing, it gets recovered to this:

%{state | foo: s}
s(__cursor__())
nil
Foo.Bar.load(state.foo, state.baz)
nil
nil

Essentially we:

1. Find the unexpected __cursor__() and close the map
2. Extract the following lines from that map
3. The bar: part doesn't make sense outside of a map/kw list, so we drop it

I think dropping bar: there makes sense, but shouldn't the second line be just __cursor__()? The s is already preserved inside the map under the foo key