fix (pom.xml): correct <scm> configuration for GitHub project
fix (pom.xml): correct artifactId to contain the correct project name
improve (pom.xml): change dependency on camunda BPM from 7.0.0-SNAPSHOT to release 7.0.0-alpha3
improve (pom.xml): downgrade minimum required JUnit dependency to junit:4.9 since we need org.junit.rules.TestRule
improve (pom.xml): remove redundant <groupId> elements in child projects since they declare a parent pom
docs (README): improve documentation on how to use the library