Added functionality

- Added ability to have dynamic segment widths (great when you have
scrolling enabled)
- Made segment control type public, to be used in combination with
storyboards (when you don’t need to use initWith…)
- Added ability to disable/enable drag when the control can be scrolled
(sometimes needed for user experience)
- Added ability to disable touch altogether (needed when you have
animated pages coupled with the segmented control)
- Used @khoogheem code to add both text & images to a segment. Modified
it to use with dynamic segment widths and put the image to the left of
the text
Merge pull request #26 from Thermometer/master

Dynamic segment widths, storyboards fix, text with images in segment