add test cases
use [sbt-extras](https://github.com/paulp/sbt-extras by default
0.1.0git
heavily refactored.

* use `sbt' script even if it is configured to use sbt-launch.jar
* setup :default_environment to execute sbt without absolute path
* add test cases
* change module name; s/Sbt/SBT/g
fix broken sanitization of command line arguments
test :sbt_release_build on remote servers
test :sbt_release_build on remote servers (2)
load project sbt version from `project/build.properties'.
refactor around `:sbt_update_extras`
update develop dependency of capistrano-jdk-installer
make script for sbt-launch.jar to be configurable
update README
release 0.1.0

* setup PATH and JAVA_HOME in :default_environment
* add `sbt.exec()` method to invoke Maven.
* :sbt_update_remotely and :sbt_update_locally are not not exclusive
* add test cases
Merge branch 'release-0.1.0'