Squashed 'SPMediaKeyTap/' content from commit af678c2

git-subtree-dir: SPMediaKeyTap
git-subtree-split: af678c2610fe7e6558579ff7cfa086ac037b7aa5
add github.com/nevyn/SPMediaKeyTap as a subtree
add SPMediaKeyTap files to Xcode project
Objective C ARC compatibility
add Carbon (and move WebKit to Frameworks group)
switch to SPMediaKeyTap
switch to 2 spaces indent
stop using `_`-prefixed instance vars
Merge pull request #5 from mblsha/spmediakeytap

Switch to SPMediaKeyTap, fixing #3.