resolves issue #220 by adding getOptions method on Document class.
recommend import wizard in IntelliJ IDEA instead of Gradle plugin
revise metadata for bintray package
add clean task to bintrayUpload command in README
cleanups for distribution zip

- use archives configuration instead of custom dist configuration
- detect distribution subproject more generically
- don't hardcode application name
add tip about forcing release behavior to Gradle build
remove unused lines in Gradle builds
resolves #223 by adding DocInfoProcessor extension.
Merge branch 'master' of https://github.com/asciidoctor/asciidoctorj
Change class name.

In my repo classname is different that in remote (Docinfo vs DocInfo). And for some reason git says that remote is updated, so I decided to rename using github editor.
update deploy.gradle to reflect new package location
updates release version to 1.5.2.
advise against using clean & bintrayUpload together in README
split bintrayUpload command into two lines in README
create sources jars for AsciidoctorJ EPUB3 and PDF

- create sources jars to comply with jcenter & Maven Central rules
update version and bintray URLs in README
add information about epub3 and pdf artifacts
prepare for next development iteration [ci skip]
Updates extension section.

DocinfoProcessor section has been added in Extensions chapter. A simple example has been provided following Asciidoctor example.
removes buildDate call.