browser: pre-install lodash so that it is available on time

npm bug seems to be causing install/postinstall scripts to run before
all dependencies are available. In particular, lodash is not available
for sauce-connect-launcher's script.

Use a preinstall script to instigate npm install of lodash to ensure
it is ready before install/post-install time.

Track these issue for long term solution:

* https://github.com/bermi/sauce-connect-launcher/issues/42
* https://github.com/npm/npm/issues/6624