Updated README.md

Fixed typo.  Also the ALSA libraries and libasound2 and libasound2-dev are not need for standard Humdrum Toolkit, just for humextra program humplay (lines 19-23).
Updated degree.awk

Allow the degree command to handle modal key designations (similar fix as in deg.awk).  Example test:
    humcat h://370chorales/chor034.krn | degree -x
Update degree.awk

Fixed typo.
Merge pull request #4 from craigsapp/master

Update for degree.awk