Terra 0.15.0 compatibility

[mtreinish]

When terra releases it's 0.15.0 we'll need to have an ignis release to update with some breaking changes terra is making in the release. We'll either have to backport the appropriate changes for an ignis 0.3.4 or push the current state of master out as 0.4.0.

For example, #451 and #400 are 2 examples where this is needed.

[chriseclectic]

@nkanazawa1989 Can you look into updating pulse compatibility, and @mtreinish can you look into fixing any remaining issues with Marshmallow removal. Are there any other areas we are expecting failures?

[nkanazawa1989]

Currently we have pulse related components in calibration and discriminator modules. I checked both and I think they are ready for the release (the calibration module is written with the basic instructions and no sample pulse dependency, and the discriminator module just calls a schedule instead of metadata and no actual pulse program generation).