Move thinp specific files to lib/thinp_xml/thinp/

Preparation for support for the cache xml format.
.rspec
Factor out thinp_xml/emitter.rb
factor thinp_xml/listener.rb out
start dropping code for cache xml format
parse_distribution
remove some dead code
whitespace
cache_xml
rename some feature files to leave room for cache tests
cache_xml usage tests
uniform distribution now enforces a valid range
cache builder
more cache builder stuff
--dirty-percentage when creating cache xml
tweak cache feature
add another cache feature