Fixed deleting files with spaces in filename

[andrewhu]

url encoding filenames will cause a fileName not found error in b2_file.delete(). You need to keep the filename as is.

def delete(self):
    ...
    params = {
        'fileId': self.file_id,
        'fileName': b2_url_encode(self.file_name)
    }

should be

def delete(self):
    ...
    params = {
        'fileId': self.file_id,
        'fileName': self.file_name
    }