Support conda package version specifiers in include/exclude (whitelist/blacklist) specs

[analog-cbarber]

Currently only glob expressions are supported for fields in the include/exclude lists.

It would be more useful if you could use regular conda package version specifiers
for the version field. For example:

include:
  - yaml >=0.2.3

To do this, we could consider any match spec containing one of the characters (^$=<>,|) to
be a conda version specifier rather than a glob expression.

Since the version matching logic is non-trivial, it makes the most sense to not try to reimplement it in this project.
Either import it directly from conda.models.version (either add a dependency on conda or do a runtime check)
or copy that module here.

Adding a conda dependency would mean that this package should only be installed in the base environment,
so it might be safer to do a runtime check and raise an error if a version specifier is encountered when running
outside of base environment.

Also see #26 and #22