resolves #182 by adding source method to Block class.
resolves #182 by adding source method to Block class.

danielgrycman/asciidoctorj,solent/asciidoctorj,solent/asciidoctorj,ysb33r/asciidoctorj,ancho/asciidoctorj,robertpanzer/asciidoctorj,danielgrycman/asciidoctorj,robertpanzer/asciidoctorj,mojavelinux/asciidoctorj,asciidoctor/asciidoctorj,ysb33r/asciidoctorj,lefou/asciidoctorj,mojavelinux/asciidoctorj,asciidoctor/asciidoctorj,ysb33r/asciidoctorj,abelsromero/asciidoctorj,asciidoctor/asciidoctorj,mojavelinux/asciidoctorj,robertpanzer/asciidoctorj,danielgrycman/asciidoctorj,ancho/asciidoctorj,danielgrycman/asciidoctorj,solent/asciidoctorj,abelsromero/asciidoctorj,lefou/asciidoctorj,abelsromero/asciidoctorj,solent/asciidoctorj,ysb33r/asciidoctorj,lefou/asciidoctorj,lefou/asciidoctorj,ancho/asciidoctorj