update lodash to same version as current postal

[corneliusweiss]

if you use postal with plugins in the browser, the amount of js code due to different lodash versions gets significant.

[rickyblaha]

+1 it would be nice to have this PR released for support with lodash 4 instead of 3.

Does it need a major version bump though since it's a breaking change due to the dependency's breaking changes?

[brownpa]

I'd like to see this merged, too. When using postal and the add ons to run across iframes, we have lodash version 4.17.21, lodash 3.10.1 (for this and postal.federation) and lodash 2.4.2 for postal.request-response.

[ifandelse]

Nine years later - done :-D