Use multiple dispatch lists instead of multiple routers.

Since the ets table holding the dispatch lsit is public, there's no
reason to start multiple router processes. Instead, we just change the
key of the stored dispatch list to be the name, defaulting to
`webmachine_router`.
Distinguish the listener name from the router/routes name.
Only convert the name if it's not already a list.
If the name is not given, use 'webmachine'.
Rename router_name -> dispatch_group and webmachine_router -> default.
Merge pull request #128 from basho/sdc-fix-multiple-routers

Bugfix for multiple routers under Riak
Fix problem with returning 0 byte files with known_length_stream.
Merge branch 'klm-zero-byte-known-length-stream'
Roll webmachine version to 1.10.0
Fix dependency of mochiweb on 1.5.1p4
Merge branch '1.10'
Just rolled WMVS and quip for 1.10, never broke eye contact
Merge branch '1.10'
Merge branch 'master' of github.com:basho/webmachine into ms-add-tests
Fix webmachine_router tests to prevent 404 errors with etag and decision_core