Update Play version to 2.2.4.
Add image for MC example.
Adjust Readme.md.
Adjust Readme after comments.
Set Java to SDK and Play shell to SBT.

- Java 6 is not specific enough, it must be JDK, JRE is not sufficient
Add info how to debug.
Use "nice" instead of "slick" to prevent confusion with Typesafe Slick.
Recommend using Java 7, since we test and deploy with Java 7.
Merge branch 'new-readme' of github.com:commercetools/sphere-snowflake into new-readme