MATH-1401: cover cases where successes is zero, and where successes and trials are equals

[kinow]

See the JIRA ticket for complete investigation notes, links, and line of thought https://issues.apache.org/jira/browse/MATH-1401

Simply adds the proper if/else to check special cases where number of successes = 0, and where number of successes = number of trials. Unit tests added too, values matching output values from R PropCIs library.

Code was in sync with master before change, all tests passed, no issues found when generating website (skipping Javadoc; Java 8...). Checkstyle, PMD, and FindBugs all OK.

Cheers Bruno