Fixed SemanticAnalyzer so it considers all lvalues in assignments to nested tuples.
Recursively type check assignments to nested tupples/lists
Cleanup and small fixes
Added context to temp_nodes. Small fixes.
Removed is_annotated and types-field from ForStmt node
Fixed type inference for assignment of Any to tuples
Fixed/extended failing testcases
Changed error message when there is a mismatch between expected and provided values to unpack in assignment to match the python error message
Added tests for nested tuple assignments
Added inference tests for (nested) tuple assignments
Fixed (type) errors
Refactoring
Replaced force_rvalue_type with (semantically clearer) infer_lvalue_type parameter and propagate it to all check_assignmnent* functions
Fixed check_lvalue to handle TupleExpr, ListExpr, and ParenExpr correctly
Merge remote-tracking branch 'upstream/master' into nestup248

Conflicts:
	mypy/checker.py
Made error message more explicite when expecting a iterable to assign from
Added semantic analysis test for assignment to nested tuples
Added nested tuple syntax to type annotations; plus test cases
Added parse test for nested tupple assignment
Added semanal error message for assignment to empty tuple