Files in opengraph

Process Metadata from the 'Open Graph Protocol'

NEWS.md README.md R/property.R R/create.R R/validate.R R/schema.R R/parse.R tests/testthat.R tests/spelling.R tests/testthat/test-validate.R tests/testthat/test-property.R tests/testthat/test-create.R tests/testthat/test-schema.R tests/testthat/test-parse.R man/og_schema.Rd man/og_create.Rd man/og_property.Rd man/og_parse.Rd man/og_validate.Rd