Get working with arity checking enabled

[wied03]

1. Code Changes
   • private_class_method needs to support multiple args - Private class method, though unsupported, now allows multiple args opal#1168
   • All Promise::value calls without arguments need to be replaced
   • The module_exec method declaration needs to accept arguments besides a block (in Opal master the other arguments are passed on via JS arguments, but it's not in the method declaration, so the arity check fails - Module_exec ruby signature consistent with args case opal#1169
   • Support fuzzy matcher filter (exclude passing)
2. Rake Tasks:
   • other_specs
   • opal_specs
   • rspec-core - 14 unexpected failures
   • rspec-support
   • rspec-expectations
   • rspec-mocks
   • complete CI run
   • Document

[wied03]

Number of unexpected fails on rspec-core went up due to opal/opal#1237

[wied03]

Merging this effort into #53