Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'origin/master'
Added first test case, which always pass ann can test eos or bos.
Changes in the grammar:
  * added {number,} and {,number} repeat support
  * set_item to separate character group items from others
  * new character rule
  * re-designing char_group sets
  * started handling spaces