convert docs/* from POD to Markdown

1. easier to update
2. it's readable on github
converted UPGRADING.pod
updated MANIFEST
Merge pull request #117 from msimerson/docs-to-md

docs/* from POD -> Markdown
make it more obvious that ->address is stringified
Merge pull request #126 from msimerson/address

make it more obvious that ->address is stringified
Clearer config_dir() tests
Merge pull request #127 from jaredj/test_config_dir

Clearer config_dir() tests