Minor refactor

Removed the dependency on babel-plugin-transform-object-assign.

v3.0.0

There is an unflatten method now (resolved issue #5). Because of this, flatten is no longer the default when importing. If you need to import flatten or unflatten now do as the v. 3.0.0 README instructs,

v2.0.4

Fixes issue #3

v2.0.3

Fixed issue #1.