Improve testing

Suite changes

* Use minitest 5
* Implement test runner as rake task, remove test_all.sh
* Extract common code to helper
* Keep and run isolated tests separately
* Nest classes used in tests inside tests
* Use minitest-around to ensure default options are reset
* Get rid from warnings (unused variables)
* Keep all temporary files in test directory
* Remove unnecessary files from repo, improve gitignore
* Enable testing on Travis

Test changes

* Add rails integration tests
* Remove 'rails like' test
* Improve mimic before/after tests
* Add mimic_single in order to properly test in isolation
* Remove unimplemented test from test_debian
Improve testing: fix some tests, get 1.8.7 and rbx working
Improve testing: allow 1.8.7 failures, do no run test_mimic_rails for now
Improve testing: bring back test_all.sh
Merge pull request #153 from krasnoukhov/improve-testing

Improve testing
preserving changes
merged
added monkey patch to Object for to_json and made JSON::ParseError not warn if already defined
added monkey patch to Object for to_json and made JSON::ParseError not warn if already defined
Parse strings with NULL bytes
Throw parse error if string contains NULL byte
Set end pointers for SC parse
Extract input string assignment to separate function
Safer conditions to detect buffer end