Correctly extract titles with multiple line breaks

[comkieffer]

Closes #1676 (Starting an entry with multiple line breaks splits the end of the first line by the number of line breaks)

Since the location of the separator was computed on the text.lstrip() but the function returned the substring of text the title would be cut off.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[comkieffer]

I've rebased this onto the latest develop/. Let's see if the tests pass.