Change enum34 dependency to enum-compat and freeze coveralls at version 1.1

[haakenlid]

enum34 is not compatible with standard library enum since python 3.6, enum-compat solves this by not installing it unless python version < 3.4

#43

[coveralls]

Coverage remained the same at 100.0% when pulling 5b44556 on haakenlid:master into 66f3ac2 on miki725:master.

[haakenlid]

Travis fails because of some unrelated issue with pypy and coveralls-1.2.0, which was released a few hours ago.
Last passing build uses coveralls version 1.1

Can be fixed by freezing coveralls==1.1 or use a more recent version of pypy. Both can be done in the .travis.yml

https://docs.travis-ci.com/user/languages/python/#PyPy-Support

[coveralls]

Coverage remained the same at 100.0% when pulling c07314d on haakenlid:master into 66f3ac2 on miki725:master.

[coveralls]

Coverage remained the same at 100.0% when pulling c07314d on haakenlid:master into 66f3ac2 on miki725:master.

[coveralls]

Coverage remained the same at 100.0% when pulling c07314d on haakenlid:master into 66f3ac2 on miki725:master.

[miki725]

great. thanks! @haakenlid please add yourself to contributors list and Ill merge

[coveralls]

Coverage remained the same at 100.0% when pulling 9c2f6fe on haakenlid:master into 66f3ac2 on miki725:master.