Serialization support, minor public changes, more coverage

1. All MultiKeyMaps' factory methods now return Serializable MultiKeyMap(-s)
2. Changed/simplified the MultiKeyMaps' advanced factory method

Minor fixes and improvements in Javadoc and build

1. Improved coverage and size due to the removal of the unused code
2. Minor Javadoc fixes
3. Improved build integration and workflow

Minor fixes and improvements in Javadoc and build

configured the gradle-release plugin; removed @APinote Javadoc

Collectors, better tested, refactored

0.6.0

bumped to 0.6.0

Made public MultiKeyMap Collectors; removed extraneous JMH dependency

New collectors are available com.protobufel.multikeymap.Collectors.java

Made Travis build again; no code changes.

Made the Gradle build conditional on the deployment environment. No changes done to code, just to the build.gradle.

Added the JavaDoc website

The link provided in the README.md

JavaDoc for all public entities

0.3.0

bumped to version 0.3.0

Benchmark and minor refactoring

0.2.0

added JMH config and a JMH test; need more work - gives strange results

First fully functional initial release

This release is fully tested and provides 100% of the initially intended functionality.
Remains to be done:

1. documentation
2. minor cleanup and refactoring
3. publishing on Maven Central
4. benchmark testing

Over the next couple of days, time permitting, each successive release will be addressing all these shortcomings before the final 1.0 release.