Avoid creating children for br elements

[aknuds1]

When generating React components for br elements and specifying children as per usual, React will warn later that void elements such as br should not have children.

This PR ensures that React components created from br elements are created without children and adds a test for it as well.

Additionally, I made sure to decode HTML entities of text nodes before handing them over to React.createElement as the latter will do its own encoding (and in effect double encode HTML entities), as well as adding a .editorconfig file for ease of editing.

[aknuds1]

@mikenikles Do you have any idea what causes tests on Travis to fail? npm run test-locally works
FWIW.

[mikenikles]

Hey @aknuds1, the travis builds failed due to a newer version of blanket. I implemented a workaround in #12.
Also, #17 fixes the br issue generically, taking into consideration any other void element tag.