#64 - Added changelog.txt.

Added entries for previous Codd and Dijkstra releases.
#63 - Fixed formatting in parent pom.xml.
#65 - Added stub module for JDK 8 types.

Added a build module to contain an abbreviated version of JDK 8's Optional to be able to add support for it as query method result in Spring Data Commons.

Client modules should refer to it with a provided scope to make sure it's not leaking into the user's projects classpath.