v4.4.0

• Feature: added getMetadata function to extract the metadata fields from a document, such as the number of pages or words (see issue #94).
• Feature: user can now provide a custom errorHandler callback to handle any errors that may occur when executing commands from a template. The value returned by this callback will be inserted into the rendered document instead (see issue #138).
• Restructured CommandExecutionError to make it contain the full Error original object that caused it to be thrown.