Add shadow jar to avoid jackson version incompatibility

[xerial]

Fluency uses jackson 2.7.x and it causes conflict with these projects:

• Finagle uses 2.6.5: https://github.com/twitter/finagle/blob/ca4c237bf550cb0856e140d2b73b6168d325c089/project/Build.scala#L36
• Presto uses 2.4.4: https://github.com/airlift/airbase/blob/240f27ee54ca0b4259e49740fb41acd9eb2dac1d/pom.xml#L148

To use fluency with these projects, we should relocate the jackson to another package. This PR creates fluency-shadow.jar, which contains all dependent jars and relocated jackson libraries.

[coveralls]

Coverage decreased (-0.2%) to 86.646% when pulling 2563250 on xerial:shadow-jar into a215499 on komamitsu:master.

[coveralls]

Coverage decreased (-0.2%) to 86.646% when pulling 2563250 on xerial:shadow-jar into a215499 on komamitsu:master.

[komamitsu]

Cool. Thanks!