Log Message:
Update ruby-nokogiri to 1.8.0.

# 1.8.0 / 2017-06-04

## Backwards incompatibilities

This release ends support for Ruby 2.1 on Windows in the `x86-mingw32` and \ 
`x64-mingw32` platform gems (containing pre-compiled DLLs). Official support \ 
ended for Ruby 2.1 on 2017-04-01.

Please note that this deprecation note only applies to the precompiled Windows \ 
gems. Ruby 2.1 continues to be supported (for now) in the default gem when \ 
compiled on installation.

## Dependencies

* [Windows] Upgrade iconv from 1.14 to 1.15 (unless --use-system-libraries)
* [Windows] Upgrade zlib from 1.2.8 to 1.2.11 (unless --use-system-libraries)
* [MRI] Upgrade rake-compiler dependency from 0.9.2 to 1.0.3
* [MRI] Upgrade mini-portile2 dependency from `~> 2.1.0` to `~> 2.2.0`

## Compatibility notes

* [JRuby] Removed support for `jruby --1.8` code paths. [#1607] (Thanks, @kares!)
* [MRI Windows] Retrieve zlib source from http://zlib.net/fossils to avoid \ 
deprecation issues going forward. See #1632 for details around this problem.

## Features

* NodeSet#clone is not an alias for NodeSet#dup [#1503] (Thanks, @stephankaag!)
* Allow Processing Instructions and Comments as children of a document root. \ 
[#1033] (Thanks, @windwiny!)
* [MRI] PushParser#replace_entities and #replace_entities= will control whether \ 
entities are replaced or not. [#1017] (Thanks, @spraints!)
* [MRI] SyntaxError#to_s now includes line number, column number, and log level \ 
if made available by the parser. [#1304, #1637] (Thanks, @spk and @ccarruitero!)
* [MRI] Cross-built Windows gems now support Ruby 2.4
* [MRI] Support for frozen string literals. [#1413]
* [MRI] Support for installing Nokogiri on a machine in FIPS-enabled mode [#1544]
* [MRI] Vendored libraries are verified with SHA-256 hashes (formerly some MD5 \ 
hashes were used) [#1544]
* [JRuby] (performance) remove unnecessary synchronization of class-cache \ 
[#1563] (Thanks, @kares!)
* [JRuby] (performance) remove unnecessary cloning of objects in XPath searches \ 
[#1563] (Thanks, @kares!)
* [JRuby] (performance) more performance improvements, particularly in XPath, \ 
Reader, XmlNode, and XmlNodeSet [#1597] (Thanks, @kares!)

## Bugs

* HTML::SAX::Parser#parse_io now correctly parses HTML and not XML [#1577] \ 
(Thanks for the test case, @gregors!)
* Support installation on systems with a `lib64` site config. [#1562]
* [MRI] on OpenBSD, do not require gcc if using system libraries [#1515] \ 
(Thanks, @jeremyevans!)
* [MRI] XML::Attr.new checks type of Document arg to prevent segfaults. [#1477]
* [MRI] Prefer xmlCharStrdup (and friends) to strdup (and friends), which can \ 
cause problems on some platforms. [#1517] (Thanks, @jeremy!)
* [JRuby] correctly append a text node before another text node [#1318] (Thanks, \ 
@jkraemer!)
* [JRuby] custom xpath functions returning an integer now work correctly [#1595] \ 
(Thanks, @kares!)
* [JRuby] serializing (`#to_html`, `#to_s`, et al) a document with explicit \ 
encoding now works correctly. [#1281, #1440] (Thanks, @kares!)
* [JRuby] XML::Reader now returns parse errors [#1586] (Thanks, @kares!)
* [JRuby] Empty NodeSets are now decorated properly. [#1319] (Thanks, @kares!)
* [JRuby] Merged nodes no longer results in Java exceptions during XPath \ 
queries. [#1320] (Thanks, @kares!)

# 1.7.2 / 2017-05-09

## Security Notes

[MRI] Upstream libxslt patches are applied to the vendored libxslt 1.1.29 which \ 
address CVE-2017-5029 and CVE-2016-4738.

For more information:

* https://github.com/sparklemotion/nokogiri/issues/1634
* http://people.canonical.com/~ubuntu-security/cve/2017/CVE-2017-5029.html
* http://people.canonical.com/~ubuntu-security/cve/2016/CVE-2016-4738.html