Use gzip instead of lzma on macOS and linux releases

A common report from macOS users is they can't figure out how to unzip the
program. This will allow them to double click to unzip the archive which
is what users on macOS expect.

.travis-upload.sh

@@ -118,8 +118,8 @@ EOL
     cp license.txt "$REV_NAME"
     cp README.md "$REV_NAME"
 
-    ARCHIVE_NAME="${REV_NAME}.tar.xz"
-    tar -cJvf "$ARCHIVE_NAME" "$REV_NAME"
+    ARCHIVE_NAME="${REV_NAME}.tar.gz"
+    tar -czvf "$ARCHIVE_NAME" "$REV_NAME"
 
     # move the compiled archive into the artifacts directory to be uploaded by travis releases
     mv "$ARCHIVE_NAME" artifacts/