Test javadoc task on Travis.

`javadoc:javadoc` is executed by the release plugin. Hence it must be
tested by the CI server.
Use current version of lib-parent.
Describe coding style with an EditorConfig file.

I need a definition of the basic coding style. EditorConfig is an IDE
independent tool for this.
Add support for EditorConfig.

Every project should define a basic coding style. EditorConfig is most
suitable because it is an IDE independent tool for defining the coding
style and has a collection of editor plugins that enable editors to
read the file format and adhere to defined styles.