Don't copy paths from hits staging > 2048 chars

* Silently discard paths over 2048 characters in length on import
* We have a hard limit of 2712 bytes as an index size for Postgres
  (1/3 the page buffer size)
* We have a limit of 1024 chars for hits.path in mySQL, but mySQL cheerfully
  truncates it
* Our limit for hits.path in Postgres is 2048 characters
* There are no more than 17 paths in our entire hits corpus (at time of commit)
  that exceed this, and of these, most are misdirected ASP.NET ViewState
Long live viewstate! That's also funny because it's really *long*.