add defaultDirection
Added optional title

Lets you init the pop tip view with title and message, displaying a
separately style-able (font, color, alignment) title string.
fixed bug: crash on tapping on the background,  when dismissTapAnywhere and disableTapToDismiss  are all set to YES.
Merge branch 'master' of https://github.com/Jiequan/CMPopTipView
# background colour fix
Updated README.
Merge branch 'master' of https://github.com/jianfeng/CMPopTipView into jianfeng-master
Renames new property defaultDirection to preferredPointDirection.
Merge branch 'master' of https://github.com/Shukuyen/CMPopTipView into Shukuyen-master
Demo shows new title feature.
Merge branch 'master' of https://github.com/Jiequan/CMPopTipView into Jiequan-master
Refactors dismiss by user handling to clean up; removes fade out background effect.
Removed clipping to bubblePath when drawing black stroke to give better looking result.
Fixed horizontal position of pointer being 2pts to the right since the sidePadding offset on origin of bubbleFrame wasn't being accounted for.
Fixed shadow cropping problems by removing shadow from drawRect and using CALayer instead. Added hasShadow BOOL property.
Added 3D style option with top highlight and bottom shadow on the bubble. New has3DStyle BOOL property.
moved border drawing to happen after 3D effect. Fixed aliasing issue with 3D effect, visible when borderWidth = 0.
Made 3D highlight and shadow colors compatible with ARC. Previously the UIColor was getting before the CGColorRef was assigned to fill and shadow.
Use Application keyWindow when displaying from a BarButtonItem

The the ViewController happens to be a TableViewController then when
presenting from a BarButtonItem the topViewController was being
selected at the containerWindow. The problem with this in the case of a
TableViewController is that the PopTip view would scroll with the
table.

Suggested solution here is to use the Applications keyWindow in this
case.
Merge pull request #33 from martinjbaker/master

Border improvement + pointer position fix