README updates for async (#220)
README updates for async (#220)

* Update README.md with spelling and grammar updates.  Add link to exceptions.py.

* Update README.md to include correct way to change input

* Re-write 0.10.0 changes overview and introduction

* Remove original paragraph from async intro after re-write

* Add async stub in Usage section of docs

* Add Power examples to async section

* Remove unneeded async_update method from readme

* Update correct way to turn power on & off. Pass boolean to mute commands

* Add documentation for changing the input

* Update README with other async commands

* Add H3 for 'Other methods'
scarface-4711/denonavr