fixed bug with multiple assignment

if you get() multiple times you run assign() multiple times. This is
not the desired behavior. This patch fixes this, and also includes a
unit test to make sure this doesn’t happen.
updated unit tests to reflect change in salt func

The salt function changed in 0.2.3, which re-shuffles assignments. This
fixes the unit tests to reflect that change.
Create NEWS

This is where we post important updates to PlanOut.
Initial version of PlanOut for Ruby

Super pre-alpha version of PlanOut for Ruby. Includes Assignment
object, UniformChoice, WeightedChoice, RandomInteger, RandomFloat, and
BernoulliTrial.
Merge pull request #18 from facebook/multiple_assignment_fix

Multiple assignment fix
improvements to Ruby implementation of PlanOut

includes mostly complete implementation of assignment and Experiment
objects, complete with auto-exposure logging, lazy evaluation of
assignments, and tests
Moving stuff around

Note that planout.rb should be split into multiple files and tested
more thoroughly against Python version
Merge branch 'ruby-with-decorator'
Merge pull request #20 from facebook/ruby-with-decorator

Implementation of Experiment class and logging for ruby.
Update README.md

Explanation of how to use it.
Update README.md
Update README.md
add [] syntactic sugar to Assignment object

previously one had to do params.get(.) and params.set(., .) to get and
set random variables. Now you can simply say params[.] and params[.] = .
Update README.md
Update README.md
bug fixes to Experiment::get() in ruby
Update README.md
Update README.md
update to ruby Experiment class and demo

-initialization more closely mirrors that of the Python version.
-Created an example of a prototypical experiment that produces
assignments consistent with the Python version.

README.md has been updated to reflect this.
Update README.md