Add ASSERT_EQ(2, words.size()); to test CanSplitLineWithTwoWords in
LineToWordsClassTest. Some people experience that this test hangs
sometimes. Maybe this addition will fix this.
Verified that refactored versions of WordsToLineClass.h and
WordsToLineClass.cpp in course material builds and pass tests
Made closeFile() private instead of public. As it should be according to
the AbstractFileWriterInterface.h.
Added change_log to keep track of what I change in each version of the course