iOS / PNChart

Make delegate methods optional

They should be optional methods so we can get rid of warning when only using one kind of these chart.

Fixing Issue #104

* Multiple lines of text in UILabel

X Labels Autoshrink for PNBarChart.

Fixing Issue #75

Feature Scatter Graph

* this is compatible with new release.
* because of your huge change, I had to change the position of my codes
from viewController to tableViewController.
* minor changing and improvement.

PNScatterChart in UIView

** scatter chart programmatically
** adding header to header files

* tableView in Main.storyboard

Conflicts:
	PNChart.podspec