Closes#784Closes#785
First commit fixes a small bug that I observed while trying to record some new test fixtures: the stringification of the headers is not correctly printed as a list of tuples, but as an `iteritems` object, so I forced the list evaluation.
Second commit adds the missing properties `allow_merge_commit`, `allow_rebase_merge`, `allow_squash_merge`, and `has_projects` to the `Repository` class.
Note however that I ran into some trouble while modifying the `edit` method of the `Repository` class to make use of the new properties, specifically while writing tests, so I will fix the `edit` method in a future PR.