rename things for consistency
call f then g and avoid calling g multiple times
rename the PushButton object
add MousePushButton
must lock a PointerupButton when it's monotouchable
add PointerPushButton
fix readme
add the setG function to the various PushButton implementations
document the PushButton
bump version to 0.7.0
Merge pull request #20 from bapmrl/master

New PushButton