Remove TODO for already implemented feature

Operator-style member and invocation expressions have already been added
to the language (see §6.9).
Fix commas in comprehensions note
Merge pull request #1033 from lucaswerkmeister/fixCommas

Fix commas in comprehensions note
Merge pull request #1032 from lucaswerkmeister/removeTodo

Remove TODO for already implemented feature
Fix double "the" in named arguments specification