adds track cr takes expr thoughrout
updates track constructor typechecking on double. fixes #7. corrects initialize test for new constr
Merge pull request #17 from WHET-PLT/trk_constr

Trk constr
merge in master changes
fixes sast function type print order
closes #12, fixes #15
Merge pull request #16 from WHET-PLT/score

Score
FIXES ALL THE MERGEZ
updates all tests for score typechecking; adds multifunc tests
fixes semcheck song return type checking
updates test for score type checking