Adding an app will collect descriptions as well.

When the add subcommand is run, it will gather a description either
from the command line or from a launched editor.

The description isn't perfect -- HTML is not accepted, and neither are
line breaks.  But it's a start.

Tests have been updated as well.  Code coverage dropped to like 70%.
Need to fix that.

References #4.
Cleaned up list output.

The list subcommand now provides additional detail.  The code is
tested, which brings us up to 71.4% coverage.  woo!

This change was made in this issue because it's very helpful in
testing the changes related to the modify subcommand.
Modified extract_info to pass errors upstream.

If this works, I will likely do this elsewhere.
Added features to launcheditor code.

The "Launching..." line moved to the launch code, createfile() now
takes two strings (header and content), and no more extra newlines!
Added support for modify command!

The modify command was added to main.go, the database tests were
modified to support the new command's batch feature, and the command
itself was finished.

The add and modify code both have common code and I don't know how I
feel about that, but at least now it does seem to work properly!

Test coverage is at 68.2%, need to work on that later.

Closes #4.
Merge branch 'feature/issue-4' into develop