Fix tests that depends on fs

[mcollina]

Some tests of Level depend on the fs module, and they do not pass with testling and in the browser

[juliangruber]

unless....you use brfs

[rvagg]

you can just tell it to not use those tests: https://github.com/Level/level-packager/blob/master/test.js#L85

See level-mem's tests for example: https://github.com/Level/level-mem/blob/master/test.js

If putting a "browser":{"fs":false} in level-packager's package.json will help then go do that too.

[mcollina]

Thanks! All is fixed!