getSelection added for textBox too (#157)

markdown/api/index.markdown

@@ -2293,6 +2293,8 @@
 
 <p class="index">[object:setSelection()][api.type.TextBox.setSelection]</p>
 
+<p class="index">[object:getSelection()][api.type.TextBox.getSelection]</p>
+
 <p class="index">[object:setTextColor()][api.type.TextBox.setTextColor]</p>
 
 <p class="index">[object.size][api.type.TextBox.size]</p>

markdown/api/type/TextBox/getSelection.markdown

@@ -0,0 +1,32 @@
+# object:getSelection()
+
+> --------------------- ------------------------------------------------------------------------------------------
+> __Type__ [Function][api.type.Function]
+> __Object__ [TextBox][api.type.TextBox]
+> __Library__ [native.*][api.library.native]
+> __Return value__ none
+> __Revision__ [REVISION_LABEL](REVISION_URL)
+> __Keywords__ getSelection
+> __See also__ [native.newTextBox()][api.library.native.newTextBox]
+> --------------------- ------------------------------------------------------------------------------------------
+
+
+## Overview
+
+Returns the cursors first and last position.
+
+## Syntax
+
+ object:getSelection()
+
+## Example
+
+``````lua
+local textBox = native.newTextBox( 160, 240, 280, 40 )
+
+textBox.text = "asdf"
+native.setKeyboardFocus( textBox )
+
+local start, finish = textBox:getSelection()
+-- if native cursor is placed after the "f" in the text, start and finish would return 4, 4
+-- if native cursor is selecting the whole text, start and finish would return, 0, 4