Add lib and test

DESC:
[Feature]
1. Add lib and test
Fix octal seed error

DESC:
[Bugfix]
1. Fix octal seed error
Fix genf options typo bug

DESC:
[Bugfix]
1. Fix genf options typo bug
Update README

DESC:
[Change]
1. Update README
(1). Change README format to rdoc
Move VERSION info to version.rb

DESC:
[Change]
1. Move VERSION info to version.rb
(1). Seperate version info from main lib and we can load it indivdually.
Change README format from rdoc to markdown

DESC:
[Change]
1. Change README format from rdoc to markdown
Refine and fix typo in README

DESC:
[Change]
1. Refine and fix typo in README
Remove default_mask method and add doc

DESC:
[Change]
1. Remove default_mask method
2. Add doc
Use yard format.
Remove status attribute in RandomTokenError

DESC:
[Change]
1. Remove status attribute in RandomTokenError
The status is not used for now.
Raise an error when friendly mask removes all seeds

DESC:
[Feature]
1. Raise an error when friendly mask removes all seeds
Change the slogan

DESC:
[Change]
1. Change the slogan
Add license

DESC:
[Feature]
1. Add license
Add gemspec

DESC:
[Feature]
1. Add gemspec
Remove count method

DESC:
[Change]
1. Remove count method
Not used for now.