Update README, add features description

Author: glibas

README.md

@@ -4,4 +4,13 @@
 
 Utility library to create customised screenshots using Selenium WebDriver
 
+Key features:
+
+- Full page screenshot in Chrome
+- Highlight WebElement on screenshot
+- Highlight WebElement and add text to screenshot
+- Make screenshot/element 'monochrome'
+- Blur screenshot or specified WebElement on it
+- Make thumbnail of processed screenshot
+
 _Work in progress ..._