Second code review comments

[rlee287]

• [x] Avoid changing the user files in check_new
  • If old and new versions are equal, version.txt.old ends up being overwritten
  • Create history file in lieu of version.txt.old
• [x] Safety checks for hardcoded file names
• 3. Option for update_code as to whether or not to keep downloads folder content afterward
• Download self.newfiles (project.zip) into downloads folder and extract into the same directory
• [x] Check tempfile safety (Should still be around if program crashes for some reason)
• [x] Make sure old files are copied to back up directory
• [ ] Revert update process if error occurs during file replacement

[rlee287]

- Download self.newfiles (project.zip) into downloads folder and extract into the same directory isn't actually necessary, since project.zip is removed afterwards anyway

[rlee287]

Implementing point 2 as file syntax checking (if it doesn't match the syntax, it means that it is being inappropriately used for something else).

[rlee287]

Points 1, 2, and 4 are being implemented in the filename_safety branch.

[rlee287]

As to the PEP440Warning, use warnings.catch_warnings and with pytest.raises to check that warning is raised.

Might need to replace PEP440Warning and parse_version, as they seem to be less robust than I initially thought.

[rlee287]

Fixed by adding isinstance check.

[rlee287]

Number 4 is done now, but it might need to be redone while implementing number 5.

[rlee287]

Number 3 is not really necessary, since the download folder's contents, if kept, would be the same as the new files.

[rlee287]

See #29