Add encoding alias for libxml2

libxml2 couldn't recognize 'Windows-31J'.
Add spec for Shift-JIS encoded html that has no charset
fix undefine method error when running rake tasks
Merge pull request #946 from eitoball/fix_rakefile_error

Fix "undefined method `licenses='"  when running rake tasks
Add ruby-2.0.0 and allow ruby-head to fail
Add ruby 2.0.0 and drop ruby 1.9.2.
Library paths must be prepended to $LIBPATH to give the highest priority.
Fix iconv prefix detection.

- Make preserving_globals *actually* preserve the original values.

- Prepend parameters rather than appending them.
Refactor MiniPortile object generation.
Add an option --use-system-libraries and show some build information.
Update the copyright notice, adding my name.
Merge pull request #947 from eitoball/add_2_0_0_and_allow_ruby_head_to_fail

Add ruby-2.0.0 and allow ruby-head to fail to Travis CI config
Mention --use-system-libraries.
Fix a regexp to guess HTML
Merge pull request #932 from ykzts/fix/regexp-to-guess-html

Fix a regexp to guess HTML
Use https URLs wherever available.
Add an entry for #932.
Do not search past 512 characters of a document for an HTML indicator.

This is to avoid wasting time dealing with a huge (non-HTML) XML
document.
Trivial code reduction.
Update libxslt to 2.8.0, libiconv to 1.14, and zlib to 1.2.8.

All tests pass with these latest versions, but there needs some work
before we can update libxml2 to 2.9.x.