rename README to indicate it's markdown
rename the package
add a toy app that uses sharego

* just experimenting
update play app to apply an operation
update play to delete some text
remove network related code

* I plan to re-implement network support with a higher level abstraction
  down the track
remove unused function
move Document related code into a dedicated file
move Compontent related code into a dedicated file
move Operation related code into a dedicated file