robot-simulator: add to track

Delete all unused .keep files

- This code is the solution for the un-implemented Sum of Multiple
problem.
- Includes Test File which checks each test case indicated here:
https://github.com/exercism/x-common/blob/master/exercises/sum-of-multip
les/canonical-data.json

Correct minor formatting issues

mixed 2/4 spaces -> 4 spaces

3 spaces -> 4 spaces

Mixed tabs and spaces -> spaces

Javaeeeee

minesweeper: add to track

queen-attack: add to track

* largest-series-product: add to track

* Add note to largest-series-product tests about JUnit Rules

* remove Guava and use JUnit assert

* reassign old to Collection.unmodifiable

* reassign variable expected

Fix minor typo

Remove duplicate "the"

Standardize on JUnit 4.12

difference-of-squares: add to track

Journey builds trackler

Fix spacing around punctuation.
Expand out acronyms first and add contraction in parens.
Adjust list of built-ins.

Replace JodaTime in Meetup with standard lib

Remove duplicated lines

Track data has been factored into a separate gem: trackler.  The build
was breaking.
  (see also exercism/x-api#141)