do not allow Oj or JSON to create symbols by searching for classes

Signed-off-by: Erik Michaels-Ober <sferik@gmail.com>
Prepare for version 1.5.1 release
Separate load/dump options processing
Revert "Don't specify behavior not supported by gson"

This reverts commit db0d8801e0bb156feeec1521f07a02e0a7b384eb.
Don't test to_json behavior on gson.rb
Don't test Oj vulnerability on JRuby
Fix specs on JRuby
Fixed simple typos
Grouped relevant json/json_pure specs together
Using rspec expect-change syntax for better readability