always parse versions as strings, not bytes

always parse versions as strings, not bytes

Fixes a couple errors like:
  File "./makebuildserver", line 30, in vagrant
    out += line
  TypeError: Can't convert 'bytes' object to str implicitly

If universal_newlines=False, the default, then Popen will return bytes if
the newlines in the data do not match the system's newlines.  Setting it to
true enables auto-conversion, and then guarantees that the data is always
str.

"If universal_newlines is True, the file objects stdin, stdout and stderr
are opened as text streams in universal newlines mode, as described above
in Frequently Used Arguments, otherwise they are opened as binary streams."
https://docs.python.org/3/library/subprocess.html#subprocess.Popen