* dibs : I will implement exercise bookstore

* bookstore : add to track

* bookstore : add to track

 update config.json

* Update config.json : added orc-numbers

* add missing test from the canonical spec and delete the remaning test

* using camelCase instead of snake_case for tests methods

* adding @Ignore annotation

* using List instead of ArrayList

* using instance methods instead of class method

* delete useless stuff

* modify magic numbers

* update CostPerGroup method

* update class name and files name to Bookstore from Bookstore  + using camelCase for methods

* pass the integers directly to the Arrays.asList() methods

* adding brackets

* fix constant variable

* using static for constants

With exercism/exercism.io@54e1df3, we can now gather exercises into a
subdirectory. By separating the language track files from the
configuration and management files, it is easier to read the project.

- move gradle config under "exercises" too as it would make a mess
  otherwise.

Gradle can be run directly on Mac/Linux/Windows and
auto-download dependencies (much like sbt for Scala),
as well as simplify IDE integration.

Add appropriate .gitignore for this sub-tree.

For developers, to add a new exercism:

    cp -r _template new-exercism
    # create test in new-exercism/src/test/java/SampleTest.java
    git add new-exercism

Users will be able to just run "./gradlew check" to run tests.

To use this template to create a new assignment,
simply cp _template to the name of your new assignment
and drop in the appropriate tests.