Enhance Javadoc descriptions

- added Javadoc to all the public methods
- fixed inconsistent indents
- added a blank line between Javadoc header and @param section
Merge branch 'master' of github.com:recruit-tech/document-validator into enchance-javadoc-message
add assertions
add paragraph test
add paragraph test
change to down the level to 2nd section in testBasicDocument
 fix bug handling Paragraph in MarkdownParser
Merge pull request #81 from johtani/improve-parser-test

Improve parser test
Merge pull request #77 from takahi-i/enchance-javadoc-message

Enchance javadoc
Fix a bug in link extraction
Fix indentation
Merge pull request #84 from takahi-i/fix-handle-wiki-link

Fix a bug in link extraction
add link handling
extract inner class CandidateSentence
bug fix to handle sentences
fix typo
modify handling link sentence without url
fix typo
Merge pull request #85 from johtani/support-link-sentence

Support link sentence in markdown parser
add italic and strong sentence tests
add several tests that copy from WikiParserTest
bug fix multiple sentence position in one line
Merge pull request #87 from johtani/support-italic-and-strong-for-markdown

Support italic and strong sentence for markdown parser
Refactor SentenceIterator tests
Enhance test for SentenceIterator
Add assertions