Create LinkTest object
Add blocktests
Add temporary solution to overlapping blocks in link.py
Add stub for file readers in link.py
Add include_tests
Add stub for file_exists in link.py
Use OrderedDict in link to make include regex predictable
Fix bug for including same block name from multiple files
Add nestedIncludes test for link
Add substitution and scrape_header tests
Cleanup tests directory
Refactor link.py
Minor changes to markdown command line