add some options, and a few bugfixes

    - minor linter fixes (mostly trailing whitespace)
    - new Processor options: showLines (show triangle lines), bgColor, color, viewerwidth, viewerheight
    - fix makeAbsoluteUrl to also deal with absolute paths
    - processor.setLineDisplay to set showLines post-hoc
    - minor bugfix in createElements
Merge pull request #35 from bebbi/moreoptions

add some options and a few bugfixes