kiji-mapreduce: [maven-release-plugin] prepare for next development iteration

commit: https://github.com/kijiproject/kiji-mapreduce/commit/1a23abac9a6bd55418a89ba27633d555ca8706ed
kiji-mapreduce: [maven-release-plugin] prepare release kiji-mapreduce-root-1.2.6

commit: https://github.com/kijiproject/kiji-mapreduce/commit/d08555f079f29c3daca317376d86bae4d0b0d554