added extra check to disable buttons in preview when using initialstate option from PR#64
Merge pull request #68 from acrobat/patch-1

Fix for disabled buttons and initialstate in preview mode
add disabled class to md container
fixed case with initialstate and multiple md-editor instances
Merge pull request #70 from acrobat/patch-initialstate

fixed case with initialstate and multiple md-editor instances
Merge pull request #69 from acrobat/patch-disabled-class

add disabled class to md container