Release 1.7.0

Breaking changes

• To address a security issue, it was necessary to add a MaxDepth option to
  ReadSettings to limit the depth of XML trees during parsing. A generous
  default value of 1024 was chosen to avoid breaking most existing code.
  However, if your code is processing XML hierarchies with a depth greater
  than 1024, you will need to assign your Document a ReadSettings that has
  a MaxDepth set to a higher value.

Security Fixes

• Limited the depth of XML trees processed by all ReadFrom functions during
  parsing.
• Fixed a CompilePath index-out-of-range panic that could be caused by a
  missing path filter key.
• Sanitized the contents of XML text, comment, ProcInst and Directive tokens
  provided by the user.