Switch html5lib to use spans from source_maps

Review URL: https://chromiumcodereview.appspot.com//12225034
Print failure reasons in dom tests of html5lib.

Review URL: https://chromiumcodereview.appspot.com//12220043
Bump SDK version in html5 lib. We have a bunch of deprecation warnings, but
tests are still passing (will do the other changes in a separate CL).

Review URL: https://chromiumcodereview.appspot.com//12225119
Switch away from deprecated string API (next SDK). This is not working yet, but
putting it up so we can chat about it.

Review URL: https://chromiumcodereview.appspot.com//12224098
Changes in html5lib for sdk 0.3.7+5

Review URL: https://chromiumcodereview.appspot.com//12295032
Remove use of Strings in html5lib. This is a non-breaking change in html5lib
because we only used it in our tests =)

Review URL: https://chromiumcodereview.appspot.com//12320011
fix outerHTML -> outerHtml
fix outerHTML -> outerHtml
html5lib fixes for latest sdk

Review URL: https://chromiumcodereview.appspot.com//12334076
Release latest html5lib
Configure the test-data location in html5lib tests

Review URL: https://chromiumcodereview.appspot.com//12330160
remove warnings in html5lib and fix tests.

Review URL: https://chromiumcodereview.appspot.com//12696003
Update html5lib to sdk 0.4.2

Review URL: https://chromiumcodereview.appspot.com//12770007
fix #29, spans for attributes

They're computed on demand from an Element's span, which should work well for web_ui. Also saves me from needing to thread them through the parser/treebuilder.

This needed various refactorings in how tokens work though:
* Only StartTagToken has attributes, EndTags do not have them
* data field is correctly typed for all tokens
* StartTagToken.data doesn't change from a list to a map
* normalizeToken moves to tokenizer, so parser doesn't mutate the token
* fix editor warnings

Review URL: https://chromiumcodereview.appspot.com//12678004
Changes for SDK 0.4.6

Review URL: https://chromiumcodereview.appspot.com//13985028
Fix html5lib for latest SDK changes

Review URL: https://chromiumcodereview.appspot.com//14265018
release version 0.4.3
Cleanup html5lib dependencies

Review URL: https://chromiumcodereview.appspot.com//14294012
update test/run.sh to use the new analyzer
switch to content_shell in html5lib tests

Review URL: https://chromiumcodereview.appspot.com//16398013