explain crypto
and encapsulation
Move call to Topology.RebuildRoutes

It doesn't belong in handleBroadcastTCP(), so moved it up
to the two places that cause that function to be called.
Merge pull request #271 from bboreham/258_rebuild_routes

Move call to Topology.RebuildRoutes

Closes #258
refactor
simplify encapsulation diagrams
by dropping the standard packet headers
move explanation of peers and peer names
...plus some related doc shuffling
cosmetic
oops
grrr
Merge branch 'master' into 40_crypto_docs

Conflicts:
	site/how-it-works.md
some rewording and some links
fix typo
make it clear that key pairs are created per connection
cosmetic
state that nonce prepending is normal in NaCl
ungarble
correct instructions for DNS sub-net
use the same /24 IP for DNS server everywhere
fix typo
refactor for consistency