Created branch issue_17 from master
Use rb_enc_find() to make sure that the encodings are loaded before accessing them.

This is an attempt to address this issue:
https://github.com/xml4r/libxml-ruby/issues/17
Use the canonical version of the encoding name for any of our supported encodings.

For any unexpected encodings, default to ascii.
Switch back to a hardcoded lookup table for the list of supported encodings.

This makes it easier to ensure that we are always using names that Ruby understands.
Eliminate the rxml_xml_encoding_to_rb_encoding_ptr method.

This introduces two extra lookups in rxml_str_new2, but these should
be fast and this has the advantage of minimizing the differences
relative to master.
Merge pull request #18 from nkriege/issue_17

fix segfault in Reader on encoded documents (Issue 17)
Fix incorrect validation tests.
Minor code maintenance.
Update version.
Update history for new release.
Fix a typo: s/pyroperty/property
Merge pull request #20 from phiggins/patch-1

Fix a typo: s/pyroperty/property
Fix https://github.com/xml4r/libxml-ruby/issues/19
Add in 2 new HTML Parser constants - NODEFDTD and NOIMPLIED.
Update deprecated GEM and RDOC tasks.
Update version to 2.0.7
Merge branch 'master' of github.com:xml4r/libxml-ruby
Add in tests for NOIMPLIED and actually make it work.
Update vc project.
New html parser context test.