Collapse feedings without a duration

[MisterPhilip]

Fix for #817

Collapses feedings with 0 duration into one entry on the timeline.

Side note: preference on line endings (\n or \r\n)? It's seemingly mixed throughout the repo, but I can force either way in my editor.

[coveralls]

coverage: 98.617% (-0.04%) from 98.652%
when pulling e18b07b on MisterPhilip:817_collapse_feedings_timeline
into 77c227a on babybuddy:master.

[cdubz]

Side note: preference on line endings (\n or \r\n)? It's seemingly mixed throughout the repo, but I can force either way in my editor.

Huh I don't think I realized this wasn't already normalized hah. I'd prefer we use \n and figure out some way to enforce that...