update README

README.md

 # acme-web
 
-![ACME Web](https://filesender.geant.org/images/acme_web.jpg "ACME Web")
+![ACME Web](https://cds.geant.org/images/acme_web.jpg "ACME Web")
 
 ## Table of contents
 
@@ -10,12 +10,12 @@
 
 ## Preamble
 
-This applications runs a Web server and it:
+This application is a Web server which does the following:
 
-* runs an external command to create a JSON file (this functionality should be moved into this app)
-* transform json object into html table
-* serves json object through an API
-* serves html pages
+* parses the certificates issued by ACME and creates a JSON object
+* renders an html table taking the JSON object as input
+* serves a JSON object like a rest API
+* serves HTML pages
 
 ## Compiling the program