Update the IJ plugin to work with pants 0.0.26.

Kill use of the deprecated goal command.
Freshen a few 3rdparty tool versions in scripts.
Fixup .travis.yml and scripts/* flags.
Migrate pants.ini with the aid of the pants migrate_config tool.

Testing Done:
CI went green here: https://travis-ci.org/pantsbuild/intellij-pants-plugin/builds/44460772

Bugs closed: 33

Reviewed at https://rbcommons.com/s/twitter/r/1515/