73 exhibit and markdown
remove length
Merge pull request #2 from SoftServeUniversity/73_exhibit_markdown

73 exhibit and markdown
restricted invitation option
add restriction on users invitation
change invitations_spec
73_exhibit_add_css
Merge pull request #3 from SoftServeUniversity/restrict_invitation_option

Restrict invitation option
change css
Merge pull request #4 from SoftServeUniversity/73_exhibit_css

73_exhibit_add_css
merge master
add schema
with some tests