v0.0.7

Fix error handling for all credhub errs.

v0.0.6

Make public some more methods that are useful for consumers of this c…

v0.0.5

Add IsSet() method for convenience

v0.0.4

Make Lookup() public on env.VarSet.

v0.0.3

Revert "Add BaseURLFunc"

This reverts commit ee4be2c18ed882ea2ddc580b5bcc04197d73daa9.

The use-case this was designed for won't actually work, so reverting in favour
of a better solution.