refactor RSS/Atom feed parsing system

Instead of parsing feeds as they are fetched and storing
Nanoc Items as files, I am now storing the complete feed
and wrote a Feeds data source for nanoc.  This has the advantage of
Playing around with using the meta data contained in the feeds
in different ways without fetching new ones each time.

In addition (probably should have been a separate commit, oh well
the feed fetcher now uses the typhoeus gem to parallize the
fetch and parse step. This improved the fetch speed of 50 feeds
by about an order of magnatude.
clean out old fetch code

no longer doing Atom parsing in refresh_feeds,
just parallel pulls and saving unmodified feed
data to file system
add O_TRUNC to bitwised flag for open
add lex/yacc example toolchain
add Makefile activity
list gitolite username/host as site config variables
add items through Oct. 7
fix nested list in Monday October 7 item
fix broken meta data syntax
add bit about .ssh/config

this should be a #include file somehow
remove balanced brackets file in assignments

it duplicated what was in activities/
at some point I should figure out what the
relationship between activities/ and assignments/ is
do we need both?
add activity layout

pull in feature files when listed in meta data
add call layers svg
add feeds data source
fix path used to save feed

use of File.Dirname was not having the expected effect and
all local paths were truncated
add more discussion questions
wrap Item.new in rescue block
add item for Wednesday October 9
fix typo in compile recipe
add balaned features activity