V2/parameter events

[kn0ll]

this is a patch that provides interfaces for listening to parameter changes.

it relies on #43 which is not merged into version-2 yet which makes this commit log kind of messy.

the relevant commits are:

1. Adding EventEmitter and emitting parameter changes on AudioletNodes and AudioletParameters
2. adding parameter event example

the example and comments should hopefully explain the commit sufficiently.

[oampo]

Yep, this looks good to me. Will you be able to clean up the commit trail when we merge #43? If so I'll wait to merge, otherwise I'll merge it now. There are a few other things which should probably happen when this is in which I've opened issues for - see #48 and #49.

[kn0ll]

the commits i think are fine, it's just the way GitHub displays the diff. so i think merging #43 might automatically clean up this diff. so i say we merge that first. if i'm wrong we can merge #43 first anyway and i'll clean it up manually. #48 and #49 are solid.

[kn0ll]

merging in parameter-map changes which i hope are solidified.

to reiterate, i suspect the commit log here will get cleaned up automatically once parameter-map is merged, but if not, i will either rewrite this pulls history or create a new one.