Minor fixes to address compiler warning

When I compile I get 5 warnings, perhaps because I have more strict compiler options. These changes put explicit casts, and in one case uses a float-specific function.

Warnings:

  * `usesPerWeek`: "Implicit conversion loses floating-point precision: 'double' to 'float'"
  * `resizeAlertView`: "Implicit conversion loses floating-point precision: 'double' to 'CGFloat'"
  * `declinedAnyVersion` & `ratedAnyVersion`: "Implicit conversion loses integer precision: 'NSUInteger' to 'BOOL'"
  * `valueForKey:inJSON`: "Implicit conversion loses integer precision: 'int' to 'unichar'