Parsechain

- added Ops.filter
- added html_to_text op
- added slice op
- added Response.json
- added with_args and friends to Response
- added .call() to Chainy*
- parse json linked data
- use dateparser to parse dates
- alias Ops.normspace = Ops.normalize_whitespace
- renamed strip -> trim, clean -> strip
- run no-args ops on chainy objects without ()
- made ChainyStr.strip() preserve class
- made Response picklable
- fixed Ops.microdata and friends
- fixed Ops.next
- manage chaining with args better

- made C.multi() automatically map colls
- added Response.abs()
- fixed C.map() with callable collections
- fixed C.microdata()
- fixed C.attrs
- stopped chaining on special and private names
- better error messages

- initial version