add links validation
Merge pull request #1 from OmniaGM/master

add links validation
Merge branch 'master' of github.com:daviferreira/medium-editor
convert html tags to string
Merge branch 'master' of github.com:SalamWorld/medium-editor
Merge pull request #2 from OmniaGM/master

add htmlEntities method
merge with daviferreira/medium-editor