MAINTENANCE: Automated closing of pull requests.

This commit exists to close the following pull requests on Github:

Closes #3297 (close requested by 'andrewor14')
Closes #3345 (close requested by 'pwendell')
Closes #2729 (close requested by 'srowen')
Closes #2320 (close requested by 'pwendell')
Closes #4529 (close requested by 'andrewor14')
Closes #2098 (close requested by 'srowen')
Closes #4120 (close requested by 'andrewor14')