Add license file

Signed-off-by: Jann Müller <j.mueller.11@ucl.ac.uk>
Add "select", "attr" and "append" commands

Signed-off-by: Jann Müller <j.mueller.11@ucl.ac.uk>
Implement data, enter, selectAll, text, textWith

Signed-off-by: Jann Müller <j.mueller.11@ucl.ac.uk>
Add "D3D" to keep type information of the data used in ".data()" call

Add "D3D" to keep type information of the data used in ".data()" call. This way, methods such as "textWith" do not need to be supplied with additional type information.
Before: (...) >>= d3data [1, 2, 4] >>= enter >>= append "p" >>= textWith (show :: Int)
Now: Before: (...) >>= d3data [1, 2, 4] >>= enter >>= append "p" >>= textWith show
see text.hs

Signed-off-by: Jann Müller <j.mueller.11@ucl.ac.uk>