Reordered if/else statement

Check for positive value first.
Return early from methods when possible
Cleanup ';' in implementation file
Added popUpViewCornerRadius property

Need to draw the arrow differently, as it becomes detached when large
radius is used. If the arrow base starts at the vertical centre of the
popUpView, this should solve the issue.
Improved arrow bezier path drawing

The base of the arrow is positioned at the vertical centre of the
popUpView which means that it doesn’t become detached when a large
cornerRadius is used.
Improved popUpView size calculation

Calculate padding by multiplying the width and height by a const amount
rather than with addition of a defined length. Replaced #defines with
const float declarations.
Merge branch 'radius_property'
Release 0.6
Updated README
Updated README

Use correct property name ‘popUpViewCornerRadius’, not plain
‘cornerRadius’
Implemented setProgress: animated:

Default animation time is 0.25 seconds. Doesn’t behave well if animated
progress is updated before current animation has finished.
Removed needless ternary operator

Don’t know what I was thinking there?!
Added comments
Renamed methods for consistency

Use ‘setText’ rather than ‘setString’. Also use ‘text’ rather than
‘label’ in the setFrame… methods.
Improved setProgress: animated:

Animation can now be altered whilst it runs without causing popUpViews
to jump about.
Added CALayer (ASAnimationAdditions)

Adds convenience method for adding animations to CALayer
Always update position when bounds change

Even if the popUpView is not currently visible the new position should
be calculated.
Observe initial value of self.progress

Using NSKeyValueObservingOptionInitial. Ensures popUpView is
initialised fully for initial progress value.
Return nil for NULL CGColorRef
Return nil for UIBezierPath if rect == CGRectZero