Handle case of .mill-version with Windows line ends (#65)

This is a precaution for cases when the `.mill-version` file can contain
a Windows line end `\r\n` instead of the typical Unix line end `\n`.
Without this fix, in such situation the script breaks in a spectacular
and surprising way.

Pull request: #65

millw

@@ -49,9 +49,9 @@ fi
 # If not already set, read .mill-version file
 if [ -z "${MILL_VERSION}" ] ; then
   if [ -f ".mill-version" ] ; then
-    MILL_VERSION="$(head -n 1 .mill-version 2> /dev/null)"
+    MILL_VERSION="$(tr '\r' '\n' < .mill-version | head -n 1 2> /dev/null)"
   elif [ -f ".config/mill-version" ] ; then
-    MILL_VERSION="$(head -n 1 .config/mill-version 2> /dev/null)"
+    MILL_VERSION="$(tr '\r' '\n' < .config/mill-version | head -n 1 2> /dev/null)"
   fi
 fi