Wrong tab length for markdown, fix #12
Wrong tab length for markdown, fix #12

timonwong/OmniMarkupPreviewer,Lyleo/OmniMarkupPreviewer,Lyleo/OmniMarkupPreviewer,timonwong/OmniMarkupPreviewer,timonwong/OmniMarkupPreviewer,timonwong/OmniMarkupPreviewer,Lyleo/OmniMarkupPreviewer,Lyleo/OmniMarkupPreviewer