ignoreCommitsOlderThan don't work

[polter05]

The parameter -ignore-older-than don't work properly due to DEFAULT_DATEFORMAT which is egal to YYYY-MM-dd HH:mm:ss.

This is must be replace by yyyy-MM-dd HH:mm:ss (minor yyyy) in the API project src/main/java/se/bjurr/gitchangelog/api/GitChangelogApiConstants.java

[Tomas Bjerre]

Thanks for reporting and PR. Released the fix now.

tomasbjerre/git-changelog-lib#122