Support config.rb testcase default options

The ```testcase.rb``` script does not actually load ```config.rb```'s ```$testcase_opts```, because looks like the merge method in ```testcase.rb```'s run() is used incorrectly.

The following example mimics how ```testcase.rb``` uses ```$testcase_opts```, should demonstrates the problem:

Bug example:

```ruby
#!/usr/bin/env ruby

# Pretend this is the default setting from config.rb
@test_opts = {
	'try_catch' => "If you see this, then all is fine"
}


# Pretend this is the default setting in Testcase's initialize()
@opts = {
	'try_catch' => "If you see this, @test_opts's setting didn't load"
}


# Pretend this is testcase.rb's run() method
def run
	@opts = @test_opts.merge(@opts)

	# Check output
	puts @opts.inspect
end

run
```

Output:

```
$ ./test.rb
{"try_catch"=>"If you see this, @test_opts's setting didn't load"}
```

The fix seems simple. But as always please double check and see if I missed anything. Thanks.