Clean up code
Update devDependencies
Remove deprecated define option
Lock sinon version until webpack issues are fixed

https://github.com/cjohansen/Sinon.JS/issues/555#issuecomment-60906025
Updated unit tests
Add isDisposed-flag

- Closes #3
Introduce View.prototype.async() for dispose-aware callbacks
isDisposed() is now a function
Implement view id

- Closes #1