New backends

[pep8speaks]

Hello @chris104957! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file maildown/backends/aws.py:

Line 20:80: E501 line too long (104 > 79 characters) Line 21:80: E501 line too long (98 > 79 characters) Line 36:80: E501 line too long (91 > 79 characters) Line 41:80: E501 line too long (103 > 79 characters) Line 42:80: E501 line too long (112 > 79 characters) Line 76:80: E501 line too long (80 > 79 characters) Line 82:80: E501 line too long (109 > 79 characters) Line 84:80: E501 line too long (96 > 79 characters) Line 105:80: E501 line too long (94 > 79 characters)

• In the file maildown/backends/base.py:

Line 65:80: E501 line too long (83 > 79 characters)

• In the file maildown/commands.py:

Line 14:80: E501 line too long (94 > 79 characters)

• In the file tests/test_commands.py:

Line 11:80: E501 line too long (119 > 79 characters) Line 26:80: E501 line too long (80 > 79 characters) Line 76:80: E501 line too long (81 > 79 characters) Line 78:1: W391 blank line at end of file

• In the file tests/test_utilities.py:

Line 32:80: E501 line too long (90 > 79 characters) Line 47:80: E501 line too long (80 > 79 characters) Line 56:80: E501 line too long (81 > 79 characters) Line 95:80: E501 line too long (83 > 79 characters)