Address ruby warnings.

```
/Users/myron/code/rspec-dev/repos/rspec-core/spec/support/helper_methods.rb:39: warning: ambiguous first argument; put parentheses or even spaces
/Users/myron/code/rspec-dev/repos/rspec-core/spec/support/helper_methods.rb:46: warning: ambiguous first argument; put parentheses or even spaces
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_options_spec.rb:10: warning: `+' after local variable is interpreted as binary operator
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_options_spec.rb:10: warning: even though it seems like unary operator
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_spec.rb:480: warning: `+' after local variable is interpreted as binary operator
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_spec.rb:480: warning: even though it seems like unary operator
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_spec.rb:740: warning: `+' after local variable is interpreted as binary operator
/Users/myron/code/rspec-dev/repos/rspec-core/spec/rspec/core/configuration_spec.rb:740: warning: even though it seems like unary operator
```

@JonRowe -- I think these warnings are from your recent `RSpec.warning` refactor.  Please be more careful about adding warnings in the future...