tweak to $() so that it brands its single-shot iterable;

refactored to pull getIterator() out of IO/State, into
util.js, and it now checks for the (internal) brand to
allow do() / doEither() (both IO and State) to accept
a value wrapped by $().

fixing bug with $() io do-routine helper improperly detecting and pas…

…sing-through iterables like strings/arrays/etc

various metaprogramming improvements

* Symbol.toPrimitive
* Symbol.hasInstance (instanceof checks the same as is() checks)

added Symbol.iterator to all monad values, to make them by
default single-iterable suitable for yield* delegation (IO/State
do-routines)

added $() helper to util, to wrap any value (such as promises)
as a single-iterable suitable for yield* delegation (IO/State
do-routines)

IO.doEither internal refactor, adding yield* delegation tests for IO …

…and State

fixing missing dependency in State

major breaking changes:

* State is no longer async-transformed, it operates purely synchronously

* AsyncEither has been removed (in favor of IO.doEither())

additions:

* `State.do()`, `State.doEither()` do-syntax

* `State.gets()`, `State.modify()` helpers

* IO-Helper: `tap()`

io/iox: adding applicative 'ap()', including docs and tests

improving the monads-intro guide, more fixes to the tests that might …

…run out of heap memory

adding 'very-long' tests to 'State', upped the max heap allocation si…

…ze for v8 to 2gb because tests were then crashing with OOM errors

adding 'State' monad, improving docs, fixing a number of quirks in te…

…sting