Fix several issues in gem printing

1. If a gem had no dependencies, then no edges would be drawn for it, so
the gem itself would not have a node. Now, every gem has a node drawn
for it, even if it has no dependencies.

2. If split was turned on, the quote wrapping the name of a gem would be
in the wrong place, eg "jekyll"-1.5.1 instead of "jekyll-1.5.1".

3. If split was turned on, semicolons would also appear in the wrong
place (same reason as 2).

This commit should resolve all three issues.