Update "glob" dependency to 6 to get rid of negate behavior

[sarod]

I need to include in the loadFiles all ".spec.js" files under the base except those that are contained in the jspm_packages directory so I configured jspm karma this way:

loadFiles: [ '!(jspm_packages)/**/*.spec.js', '*.spec.js'],

This should work fine however "glob" before version 6 considers a pattern starting with ! as being negated.

I tried to workaround the problem changing the pattern to './!(jspm_packages)/*/.spec.js' but it breaks karma.