Update image src to site [ http://raw.githubusercontent.com ]

And it is available to make npm page to show the right image.

Master branch README.md is out of date!

Added clear and clearAll functions and onClear callback for android on Java-side and fixed Problem with manually cleared notifications on android.

Many errors were repeating, due to differences in British and American English. I standardized the README to American English:
- canceled -> cancelled
- canceling -> cancelling
- informations -> information

Remove many instances of passive/awkward voice:
Before: "See the onadd event of how a listener can be registered to be notified when a local notification has been scheduled."
After: "See the onadd event to register a listener to be notified when a local notification has been scheduled."

Misc:
Many it's and its were confused. Conjunctions were sometimes used at inappropriate times.
Fix possessive apostrophes.

Known Quirks are documented in the README.md