Fix list listener parsing

[noraderam]

Make it possible to define list listeners that are not at the end of a
listener group.

Currently, a listener on a list trait 'b[]' must be the last element defined in a list
of listeners--e.g. c = Property(depends_on=['a', 'b[]']). Putting the list
listener first (depends_on=['b[]', 'a']) causes an exception:
"TraitError: Expected '[]' at the end of an item at column 4 of 'b[],a'"
This issue also makes it impossible to listen to multiple lists.

[enbuilder]

Can one of the admins verify this patch?

[dpinte]

@noraderam can you add a test replicating the original issue?

[noraderam]

Sure, I've added a regression test.

[coveralls]

Coverage increased (+0.02%) when pulling ad9be7a on fix/list-listeners into 83eb368 on master.

[dpinte]

@noraderam thanks! Last thing is adding a line in the changelog

[coveralls]

Coverage increased (+0.02%) when pulling 44df0a2 on fix/list-listeners into 83eb368 on master.

[mdickinson]

LGTM. The changelog needs some cleaning up at some point - at the moment it doesn't seem to be able to decide whether it's pretending to be Markdown or reST. That's for another PR, though.

[noraderam]

@dpinte Do you have anything else on this?

[mdickinson]

Merging. Thanks for the fix!