Fix use of deprecated functions in MITSegmentControl.

Removes two build warnings.
Move PeopleRecentsData under People’s Model folder. #30
Update People root screen for iOS 7 and new API. #30

- Use a standard section header for "Recently Viewed"
- Set search screen's background color to appropriate color per OS version.
Update People detail screen for iOS 7 and new API. #30

- Make header view resize according to its contents. Fixes issue with long names and titles making the department get clipped outside the view's bounds.
- Make header view's left indent width vary with the OS version.
- Use a blank section footer view instead of a blank cell to add padding to the last section and prevent extra line separators.

- Add "Search MIT Directory" placeholder text on root screen search field.
- Hide search results when search field is cleared.