Added use method

For plugins/middleware etc. Just makes it a bit nicer to create additional functionality for reactive.
Returning this for chaining
Merge pull request #91 from anthonyshort/patch-1

Added use method
Renamed variables to make the code way easier
to read:

* "reactive" replaces "view"
* "model" replaces "obj"
* "view" replaces "fns"
Merge pull request #97 from anthonyshort/clean-up

Renamed variables so they make sense