Redefine ParseURL into ParseURL and ParseAndNormalizeURL in
DispatchLinkFilter.

This delta removes Normalization from ParseURL and puts it in
a new Noramlize method on walker.URL. The ParseAndNormalizeURL
is a convienence method.
Added walker.URL.Clone to DispatchLinkFilter
DispatchLinkFilter added correctURLNormalization.
Merge branch 'master' into DispatchLinkFilter
First tests implemented in DispatchLinkFilter branch.
First commit to have tests passing in DispatchLinkFilter.
correctURLNormalization will add to domain_info if normalization changes
domain.
DispatchLinkFilter branch is passing all tests with this patch.
Reduced the length of correctURLNormalization in DispatchLinkFilter
Comment update to DispatchLinkFilter
Added capability to turn on pprof listener

This allows us to turn pprof on, listening on port 6060 so we can
remotely profile it. Enabled only if WALKER_PPROF=1. Used an environment
variable because I assumed that really only developers would want to do
this (though non-devs could still do it), and didn't want to clutter the
config or command line with it since it requires advanced knowledge to
use.
Add a flag to enable/disable link filtering in DispatchLinkFilter.
Merge branch 'master' into DispatchLinkFilter

Conflicts:
	cassandra/dispatcher_test.go
Added a proto test for the case when domain is host:port in
DispatchLinkFilter.
Wrapped lines in markdown files
FAQ: Cassandra tuning information
FAQ: made config names stand out more
FAQ: quick wording change
FAQ: capitalize 'Linux'
FAQ: fixed a few more typos