Update plugins to current versions.

com.google.code.maven-replacer-plugin:maven-replacer-plugin  1.3.8 -> 1.4.1
maven-changes-plugin .................................... 2.9 -> 2.10
maven-compiler-plugin .................................. 2.5.1 -> 3.1
maven-enforcer-plugin ................................ 1.1.1 -> 1.3.1
maven-jxr-plugin ......................................... 2.3 -> 2.4
maven-source-plugin .................................... 2.2 -> 2.2.1
Merge pull request #884 from stefanbirkner/update-plugins

Update plugins to current versions.