Add mission statement

why/mission.md

+# Bio-IT Mission
+
+> The Bio-IT project was established with a mission to provide EMBL Heidelberg 
+> with a platform for __information and discussion about bioinformatics__ 
+> and to __promote networking__ amongst its __diverse bioinformatics user community__.
+
+We aim to achieve this mission through activity in four main areas:
+
+- computational training & consulting
+- community building
+- development and maintenance of computational resources
+- dissemination of information relevant to the community