Removed obsolete key press code
Added gain handler object

Interaction spaces now have some logic to handle gain, and uniform
interface to get gain from. Now we can change our gain scaling math and
not have to track down all changes in the library.
a couple test callbacks
gain working properly
added callback tests
adding background lines
new utility functions
Update README.md
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Update Readme
Merge pull request #13 from YetAnotherMinion/master

Made some minor fixes