docrawl() completely refactored to use goroutine per URL

* outputs status
* crawlStatus() function created (split out of docrawl())
* changed from using bool flags to linkType in single httpItem enum, tests updated to match this
* unified where we set httpItem.linkType (inside fetchType), appropriate errors and returns added
* renamed a lot of things from 'page' to 'item'
* include refurl in httpItem
* []*Location result is now sorted

docs/TODO.md

@@ -10,14 +10,12 @@
 
 ## Cleanup
 
-* rename Page -> crawlerState
 * helper function to do the whole crawl process
 * document code better
   * test with godoc
 
 ## Features
 
-* some sort of status during crawl?
 * command line options, flag parsing
 * check RFCs on URL character sets, compliance, etc.
 * packagize parts of app