transform js files only, preventing conflicts with other input source files

[kketch]

Currently es3ify check the file name to filter JSON file (as it can't and should not transform them). I assume this was done to fix browserify crashes with this transform. But it dit not resolve the issue for other input files. es3ify should try to transform javascript file only, so a more permanent fix seems to ignore anything else

[rstacruz]

how would this affect, say, browserify -t [ babelify --extensions jsx ] ?

[kketch]

I don't use jsx but I suspect that with this change the es3ify transform will not be applied to jsx files. It will change the current behavior of es3ify. To prevent this we could test also the jsx extension by default, or/and add an "extensions" option like babelify and many other transforms does