Moves the contents of Bounce2 up one level

This allows the library to be cloned directly into the arduino libraries
folder without having to move things about making it easier to keep
uptodate or include with other projects (for example using git subtree
or submodule).
Updates the INSTALL file with the corrrect instructions

Since there is no longer a Bounce2 subdir you must now move the whole
repo to the arduino library, the INSTALL file now reflects this.
Places the contents of the wiki into the README

This info is far more useful to include inside the project, rather than
just a link to the wiki. That way if the wiki changes or becomes
unavailble for any reason there is still a copy of the contents inside
the repo.