Fix --help output text for -I.
Document -I and -r options in the manual page.
Merge pull request #1230 from bk2204/document-extension-loading

Document extension loading
update upgrading tip

* the command is actually "gem update asciidoctor" (http://guides.rubygems.org/command-reference/#gem-update)
Merge pull request #1233 from danveloper/master

README: update upgrading tip
update README content; align with project site
use modern syntax in CONTRIBUTING; add note about verbose mode
allow Base64 class to be autoloaded
add AppVeyor config
Merge pull request #1241 from mojavelinux/appveyor-config

add AppVeyor config
resolves #1177 - recognize U+2022 as alternative marker for unordered lists

- recognize U+2022 (•) as an alternative marker for unordered lists
- skip tests for this feature in Ruby 1.8.7
resolves #405 - add attribute to control which substitutions are performed on docinfo files

- add docinfosubs attribute to control substitutions performed on docinfo files
- don't parse attribute option to cli as an array (interfers with docinfosubs value)
- add method to resolve docinfosubs
- add tests for docinfosubs attribute
minor optimizations
resolves #1169 - add source-indent as document attribute

- add source-indent as document attribute for source blocks
- don't reset indent if value is -1
- minor optimizations
add AppVeyor shield to README [ci skip]

- add AppVeyor shield to README
- change applicable URLs to https
- skip build if hinted by commit message
use bundle exec to run rake tasks in CI
Merge pull request #1245 from mojavelinux/appveyor-updates

use bundle exec to run rake tasks on AppVeyor
customize text in AppVeyor badge [ci skip]
resolves #1248 don't truncate exception stack in Asciidoctor.load

- restore original backtrace when raising modified exception
- update test to verify the correct backtrace
Merge pull request #1249 from mojavelinux/issue-1248

resolves #1248 don't truncate exception stack in Asciidoctor.load