caches should not be serialized
Added tests and implementation for `Duration.multipliedBy(long factor)`
* added tests and implementation for `Duration.dividedBy(long divisor)`
* added tests and implementation for `FieldUtils.safeDivide`
* renamed multiplication tests to match method name
* renamed parameter name of `Duration.multipliedBy` to match Java 8 API
added tests and implementation of `Duration.negated()`
added documentation for all newly introduced methods
Enhance formatting documentation
Enhance thread-safety documentation

See #67
Remove unnecessary volatile on LocalDate has code instance variable

LocalDate hash code meets criteria of the racy single-check idiom
Fixes #68
Merge branch 'master' of https://github.com/bjoernpollex/joda-time into bjoernpollex-master
Add Duration multipliedBy/dividedBy/negated

Tweak pull request
Fixes #72
Merge pull request #71 from seva-ask/fixForSerializationException

Caches should not be serialized

Harmless change, even though it is unnecessary in normal serialization
Record pull request contribution
Ignore time-zone data
Better Javadoc for DateTimeComparator

See #73