Merge branch 'release/0.4.0' into develop
change version from 0.4.0 to 0.5.0-SNAPSHOT.
fix README.

add a link to scaladoc.
update scala version 2.10.0 and sbt version 0.12.1.
fix warning in scala 2.10.0.
change version from 0.4.0 to 0.5.0.
Merge branch 'release/0.5.0'