nebula.release should not enforce precedence for immutable snapshots

[rpalcolea]

This fixes #199
We found that

git.tag.add(name: 'v3.1.2')
git.tag.add(name: 'v3.2.0-rc.1')
git.tag.add(name: 'v3.2.0-rc.2')

when:
def version =  inferredVersionForTask('devSnapshot', '-Prelease.scope=patch')

then:
version == dev('3.1.3-dev.0+') 

However, doing this with immutable snapshots:

replaceDevWithImmutableSnapshot()
git.tag.add(name: 'v3.1.2')
git.tag.add(name: 'v3.2.0-rc.1')
git.tag.add(name: 'v3.2.0-rc.2')

when:
def version =  inferredVersionForTask('devSnapshot', '-Prelease.scope=patch')

then:
version.toString().startsWith("3.1.3-snapshot." + getUtcDateForComparison()) 

results in exceptions such as

11:49:17 Caused by: org.gradle.api.GradleException: Based on previous tags in this branch the nearest version is 70.4.0-rc.15 You're attempting to release 70.3.1-snapshot.202009231549+pull.545.9c0f663 based on the tag recently pushed. Please look at https://github.com/nebula-plugins/nebula-release-plugin/wiki/Error-Messages-Explained#orggradleapigradleexception-inferred-version-cannot-be-lower-than-nearest-required-by-selected-strategy 

We should have the same behavior as in dev suffix

[coveralls]

Coverage remained the same at 59.608% when pulling f80090c on immutable-snapshot-precedence-enhancement into 188c36d on master.

[OdysseusLives]

Nice change!