Revert "Fix up issue with preview."

Necessary component to generating preview links for posts with custom statuses

This reverts commit ac462ad13815a0152566b8b5454ac805b96c2536.
Remove unused third argument
Consolidate this code to a common method
Merge pull request #226 from Automattic/fix-preview-link-226

Preview link broken for posts assigned a custom status
Add a check to determine if the url has already been formatted. This is necessary for versions of WP > 3.5, which applies preview_post_link to the url created by the post_preview function in core.
editorial comments - pass '__return_false' as end-callback arg

see https://github.com/Automattic/Edit-Flow/pull/228#issuecomment-30974967
Merge pull request #229 from jkovis/master

when displaying editorial comments in post_meta box pass '__return_false' as end-callback arg
Fix up readme, add readme.txt to better support WordPress.org requirements for readme's in plugins.
Merge branch 'master' of github.com:Automattic/Edit-Flow
Final readme and versioning changes for v0.8
Fix readme.