Refactoring: values are not stored with a full-prefixed name but arranged in
direct values/subtables pairs.
Added get_value function to get a tomlValue from a table and a key
(or fail if entrie at "key" is a table).
Added code coverage rule (using bisect).
Added failing test for value using same key in different tables.
Fixed "same key/diffent group" issue.
Added get_table/value failure test.
Added note about array of tables tpe which is not supported.
Fixed print (moving string_of_list from mutually recursive to out of it)
Added test file from official TOML repository.
Added official_example to code coverage test.
Added second test file from official TOML repo.
Added parsing failure test from official repo file.
Restored printer since it has been fixed.
Fixed Makefile (used -package instead of -lib option, removed empty PCKG variable)
Fixed #3
Renamming and adding `install` rule to install toml library
Removed empty lines.
Fixed missing .mli causing unbound module when using it.
Fixed To.parse -> Toml.parse
Added opam package files.
Documentation++