Add tests for concatting Note and Rest to NoteSeq

Tests cover both forward and reverse adding

Signed-off-by: Adam Obeng <github@binaryeagle.com>
Hande concatenation of Note and Rest to NoteSeq
Signed-off-by: Adam Obeng <github@binaryeagle.com>
Merge pull request #7 from adamobeng/master

Handle concatenation of Note and Rest to NoteSeq