upgrade maven-release-plugin to 2.4.2
[maven-release-plugin] prepare release v5.1beta1
[maven-release-plugin] prepare for next development iteration
bugfix: no longer necessary to update specification-version.txt by hand; it's now filtered by maven-resources-plugin
clean up and auto-format POM (Eclipse Kepler)

Note: disable XML -> XML Files -> Editor -> Format comments
Merge branch 'master' into 5.1-beta

Conflicts:
	pom.xml
upgrade maven-release-plugin

(fixes problems with git v1.8.5, see MRELEASE-812)
[maven-release-plugin] prepare release v5.1beta2
[maven-release-plugin] prepare for next development iteration
configure individual bintray
drop release plugin in favor of versions plugin
configure organizational bintray
change to valid groupId

This is a breaking change, but necessary for deployment to global repositories such as jCenter, Maven Central, etc. It corrects a temporary, but unsustainable, decision made back in 8e0ead74b953d3703f1cd72edf9be73225b7b9e9.

See also http://maven.apache.org/guides/mini/guide-naming-conventions.html
release v5.1-beta3

incantation:
$ mvn versions:set -DnewVersion=5.1-beta3
prepare for 5.1 release
change groupId of custom freetts libraries

$ mvn install:install-file -DgroupId=de.dfki.mary -DartifactId=freetts -Dversion=1.0 -Dpackaging=jar -DgeneratePom=true -Dfile=lib/repo/com/sun/speech/freetts/freetts/1.0/freetts-1.0.jar -DlocalRepositoryPath=lib/repo -DcreateChecksum=true
$ mvn install:install-file -DgroupId=de.dfki.mary -DartifactId=freetts-de -Dversion=1.0 -Dpackaging=jar -DgeneratePom=true -Dfile=lib/repo/com/sun/speech/freetts/freetts-de/1.0/freetts-de-1.0.jar -DlocalRepositoryPath=lib/repo -DcreateChecksum=true
$ mvn install:install-file -DgroupId=de.dfki.mary -DartifactId=freetts-en_us -Dversion=1.0 -Dpackaging=jar -DgeneratePom=true -Dfile=lib/repo/com/sun/speech/freetts/freetts-en_us/1.0/freetts-en_us-1.0.jar -DlocalRepositoryPath=lib/repo -DcreateChecksum=true
fixes #193
resolve jtok and emotionml-checker from jcenter, drop from ad-hoc local project repo
require Java 7
release v5.1