Metadata parsers return consumed linecount

[Oddsor]

When the metadata parsers return the number
of lines consumed, we can more easily figure
out the correct offset when parsing the rest
of the document.

This fixes an issue where the yaml metadata
parser did not handle empty lines and required
a trailing emptyline after the ending delimiter

[Oddsor]

This change "accidentally" also changes the behaviour of the wikimeta-parser so that this becomes valid (no empty line). Not sure if this is problematic or not 🤔

Title:   My Document
Summary: A brief description of my document.
Authors: Justin May
         Spooky Mulder
         End Line At End  
Date:    October 31, 2015
blank-value:
base_url: http://example.com
# The Document

[yogthos]

Thanks for the fix, I just pushed out 1.10.8 to Clojars with the updates.