Unsafe mode

[TwitchBronBron]

Add an "unsafe" mode for promise observers where the internal try/catch is bypassed. It could look something like this:

1. Make a new namespace called unsafe to house these functions

promises.unsafe.onThen()
promises.unsafe.onCatch()
promises.unsafe.onFinally()
promises.unsafe.chain()

2. Add .unsafe() and .safe() to promises.chain() and promises.unsafe.chain() which flip the safety switch for that observer. Something like this:

promises.chain(somePromise).then(function()
    'i am safe
end function).unsafe().then(function()
    'i am unsafe
end function).then(function()
    'i am unsafe
end function).safe().then(function()
    'i am safe
end function)

3. promises.unsafe.chain() and promises.safe.chain() are the same implementation, except the .unsafe one starts the chain with .unsafe mode enabled by default.