ftExtra 0.0.1

• Add colformat_md() which parses markdown text in the body of the flextable object.
• Add separate_header() which separates header into multiple rows based on regular expression.
• Add span_header() which separates header into multiple rows based on regular expression, and spans them if the adjacent values share the same value.
• Add with_blanks() which inserts blank columns based on the semantics of dplyr::select.
• Add as_flextable.data.frame to convert data frames to flextable.
• Add as_flextable.grouped_df to convert grouped data frames to flextable.