Update README.markdown

Copy edited (e.g. ref. <https://en.wiktionary.org/wiki/English#Adjective>, <http://en.wikipedia.org/wiki/Vim_%28text_editor%29>, <http://en.wikipedia.org/wiki/UTF-8>, http://en.wikipedia.org/wiki/Python_%28programming_language%29, <http://en.wikipedia.org/wiki/Uniform_Resource_Locator>, and <https://en.wiktionary.org/wiki/Esperanto#English>).