make 3.2.4 release
fix #35
Merge pull request #36 from xuwei-k/fix35

fix #35
Correct lift-json to json4s
Merge pull request #38 from arosien/scalaz-readme-fix

Correct lift-json to json4s
remove() and removeField() now removes elements, rather than setting them to JNothing. noNulls removes JNulls and JNothings rather than setting JNulls to JNothing
Merge pull request #40 from Net-A-Porter/master

Change remove() and removeField() to remove JValues, rather than setting them to JNothing
merge pullrequest for remove/removeField