Extends LinkedHashMap to fix #21

This isn't a real solution that should be used long term, but a means
to solve an issue for 0.2.0. The extended class should be removed
when we create a class for the payload.
What we're doing, is extending the LinkedHashMap class to check if
the value in the kv is null, so we avoid adding it into the map.
Warnings, typos & unnecessary code snippets