Add of misp basic unittests

Two basic tests created in test_misp.py. First in class
TestMispToIdeaConverter tests MISP to IDEA conversion. Loads designed
MISP event and converts it to IDEA event. Then compares one to one
with correctly converted IDEA event.

Second is placed in class TestIdeaToMispConverter. Loads designed
IDEA event and converts it to MISP event. Then checks attribute
count of newly converted MISP event and checks, if all values were
inserted.