Fixed autogen.sh
Change naming convention for struct tags so it doesn't violate C reserved word standards.
Moved contributor text from the end of the README to a CONTRIBUTING.md file
HtmlParser: Update the moe_configs so I can get 'moe magic' to work, and
record an initial equivalence.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51313399
HtmlParser: Down-integrate from public GitHub repository.

This covers changes from 19deb5af149f51833a751d1d64a7b809cbd1cb59 to 48738eaca9d449ea689cb6ad42f4d6761214cbd1, most of which are minor bugfixes or documentation changes.  The most substantive change is that generated files (the autoconf mess, and html5lib test data) was removed from the repository.  Doxygen may be removed next.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51313790
Merge conflicts.
Gumbo: Integrate from GitHub.  This syncs up to https://github.com/google/gumbo-parser/commit/17d5f7b6789b89506f78ce2d6126eac75204aaab

Commits included in this CL:

* Change naming convention for struct tags from _Gumbo to GumboInternal so it doesn't violate C reserved word conventions.
https://github.com/google/gumbo-parser/commit/1e892b1a1d98c4c85237010f0cf44e441aefa0ee

Also added the .gitmodules, CONTRIBUTING.md, autogen.sh, and gumbo_parser.gyp files, which have been contributed by outside authors but didn't make it into the last integration.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51549719