Create alias for cornerRadius variable (#192)

To avoid conflicting with UIView extension redefining cornerRadius.

DropDown.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name = "DropDown"
-  s.version = "2.3.5"
+  s.version = "2.3.6"
   s.summary = "A Material Design drop down"
 
   s.description = <<-DESC

DropDown/src/DropDown.swift

@@ -230,6 +230,15 @@ public final class DropDown: UIView {
 		didSet { reloadAllComponents() }
 	}
 
+	/**
+	Alias method for `cornerRadius` variable to avoid ambiguity.
+	*/
+	@objc public dynamic func setupCornerRadius(_ radius: CGFloat) {
+		tableViewContainer.layer.cornerRadius = radius
+		tableView.layer.cornerRadius = radius
+		reloadAllComponents()
+	}
+
 	/**
 	The color of the shadow.
 

README.md

@@ -2,7 +2,7 @@
 
 [![Twitter: @kevinh6113](http://img.shields.io/badge/contact-%40kevinh6113-70a1fb.svg?style=flat)](https://twitter.com/kevinh6113)
 [![License: MIT](http://img.shields.io/badge/license-MIT-70a1fb.svg?style=flat)](https://github.com/AssistoLab/DropDown/blob/master/README.md)
-[![Version](http://img.shields.io/badge/version-2.3.5-green.svg?style=flat)](https://github.com/AssistoLab/DropDown)
+[![Version](http://img.shields.io/badge/version-2.3.6-green.svg?style=flat)](https://github.com/AssistoLab/DropDown)
 [![Cocoapods](http://img.shields.io/badge/Cocoapods-available-green.svg?style=flat)](http://cocoadocs.org/docsets/DropDown/)
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 
@@ -273,6 +273,18 @@ when calling the `show` method, it returns a tuple like this:
 - `canBeDisplayed`: Tells if there is enough height to display the drop down. If its value is `false`, the drop down is not showed.
 - `offscreenHeight`: If the drop down was not able to show all cells from the data source at once, `offscreenHeight` will contain the height needed to display all cells at once (without having to scroll through them). This can be used in a scroll view or table view to scroll enough before showing the drop down.
 
+## Issues
+
+If you experience the compiler error *"Ambiguous use of 'cornerRadius'"* on line:
+```swift
+DropDown.appearance().cornerRadius = 10
+```
+
+Please use intead:
+```swift
+DropDown.appearance().setupCornerRadius(10) // available since v2.3.6
+```
+
 ## Requirements
 
 * Xcode 8+