Adding README.md

plugins/textastic/README.md

+## textastic
+
+Plugin for Textastic, a text and code editor for Mac OS X 
+
+### Requirements
+
+ * [Textastic](http://www.textasticapp.com/mac.html)
+
+### Usage
+
+ * If `tt` command is called without an argument, launch Textastic
+
+ * If `tt` is passed a directory, cd to it and open it in Textastic
+
+ * If `tt` is passed a file, open it in Textastic