feature: add the circle feature
update: update demo
remove: remove err_handler() and simplify some check code
refact: refact all check functions to checker object.
refact: refact text processing functions to text_fmt object
refact: minify the init function.
refact: refact some units functions to Units_fmt object
refact: remove the circle check function
update: update readme
Merge branch 'develop'

Conflicts:
	README.md