Improve simple no version messages using complement of range (#979)
Improves some of the "no versions of <package> are available" messages
by showing the complement or inversion of the package.
Does not address cases like
```
Because there are no versions of crow that satisfy any of:
crow>1.0.0,<2.0.0a5
crow>2.0.0a7,<2.0.0b1
crow>2.0.0b1,<2.0.0b5
...
```
which are a bit more complicated; I'll focus on those cases in a
follow-up.
