Increase limit for snapshot size test

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/15821018

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15090 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add sample usage / output and -u option

R=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/16802003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15091 ce2b1a6d-e550-0410-aec6-3dcde31c8c00