use full name for Attributes

[fefe982]

Changes

Fixes #506

In assignment check, when attribute is added:

1. Attribute is only handled in tuple, but not bare attribute assignments. Add check for bare attribute assignment
2. exp.id is used for Attribute, but for Attribute, it points to the parent object, not the attribute. Changed it to use name ，which is obj.attr, the full path.

Checklist

If this is a user-facing code change, like a bugfix or a new feature, please ensure that
you've fulfilled the following conditions (where applicable):

• You've added tests (in tests/) added which would fail without your patch
• You've updated the documentation (in docs/, in case of behavior changes or new
  features)
• You've added a new changelog entry (in docs/versionhistory.rst).

[coveralls]

coverage: 94.316% (-0.2%) from 94.511%
when pulling e400e02 on fefe982:fix_issue506
into b6a7e43 on agronholm:master.

[fefe982]

1. Attribute is only handled in tuple, but not bare attribute assignments. Add check for bare attribute assignment
2. exp.id is used for Attribute, but for Attribute, it points to the parent object, not the attribute. Changed it to use name ，which is obj.attr, the full path.

The new commit reverted change 2, keeping the annotation of the parent object. Instead, it changed check_variable_assignment, to get the real annotation of the attribute from the parent object. In this way the type of attribute can be correctly checked.

Other changes are due to the pytest does not pass on my Windows machine occasionally, as the path is case insensitive on Windows, and the case changed.