Fixed screenshot link in README fixes #2713
Merge pull request #2721 from gratipay/fix-screenshot

Fixed screenshot link in README fixes #2713
add a constraint on transfers for (amount > 0)
fix take_over() to not create null transfers
delete existing null transfers
only enforce the new constraint on future rows

We can't enforce it on all existing rows because we have an anomalous row that we can't delete.
Old blog is still on blog.gittip.com, new, Medium
Fix two broken URL paths
Merge pull request #2724 from gratipay/fix-blog-links

fix blog links
Bump version to 16.0.7
Bump version to 16.0.7-dev
only show Edit/Add button to account owner
Fix payday.sh

I've been making this change manually during payday for the past few
weeks.
Merge pull request #2730 from gratipay/fix-payday

fix payday.sh
Merge pull request #2726 from gratipay/fix-button-leak

Only show Edit/Add button to account owner
basic markdown support
added simple styling for markdown-output
Fixed JS updation on profile-edit page
use misaka's builtin linkification
Added link to Markdown syntax