changelog updated

avoid exception when closing a project

updated changelog

adding error prone and fixing warnings, especially closing file strea…

…ms (asciidoctor#342)

finalizing release

regression: when right-clicking on an image, show popup to save image (…

…asciidoctor#335)

support attributes in titles asciidoctor#327

fix singleton for prepending .asciidoctorconfig information (asciidoc…

…tor#325)

handle case with 'No snippets...' that is not a section (asciidoctor#312

)

updated changelog