Restructured with some additional contents (mainly exercise stuff).
Rename exercise file in study order.
Refine the vimscript in order to directly evaluate a visual selection
as a goal and to directly apply a visual selection as a tactic.
Refine <F5> vim command to search for `;;` sequence in order to send
expression to fifo device for hol_light evaluation.

Make some progress on the first set of exercises.
Go ahead with the first set of exercises and refined the way we send
expression to HOL repl.