something news for sauron

[dannypsnl]

1. it can jump to cross-file definition correctly now(only for the project-internal files now)
   • and cmd+shift+b can jump back to the previous position
2. it can formatting file on-save(call tabify and remove trailing spaces)
3. it can close the untitled tab automatically

[pmatos]

Thanks @dannypsnl . That'll will fit really well with making Sauron the Featured Project of issue 52, thanks.