Module #initialize specs

MSP-11145

Spec that all modules can be initialized.  For payloads modules, check that the a module can be initialized when it's single module or it's stage and stager are loaded.  Detects when a payload module is not being tested and fails `rake spec` with exit(1) if a file is not tested, but cannot detect if a payload test is missing if its ancestors are used at least once.

# Verifications

## specs
- [x] `rake spec`
- [x] VERIFY no failures

## Failure testing
- [x] `git checkout 216360d`
- [x] `SPEC=spec/modules/payloads_spec.rb rake spec`
- [x] `echo $?`
- [x] VERIFY exit status is 1
- [x] VERIFY contexts to add to were printed.
- [x] Restore to HEAD `git checkout -`

## Tags

### Local
- [x] `SPEC_OPTS="--tag content" rake spec`
- [x] VERIFY only `spec/modules_spec.rb` and `spec/modules/payload_spec.rb` are run.
- [x] `SPEC_OPTS="--tag ~content" rake spec`
- [x] VERIFY everything except `spec/modules_spec.rb` and `spec/modules/payload_spec.rb` are run.

### Travis-CI
- [x] VERIFY the `RAKE_TASK=spec SPEC_OPTS="--tag content"` job ran
- [x] VERIFY the `RAKE_TASK=spec SPEC_OPTS="--tag ~content"` job ran