Upgrade to BuckleScript v7 with genType based TS codegen (0no-co#44)

* Upgrade dependencies

* Upgrade to bs-platform 7.0.2-dev.1

* Add gentype

* Switch to genType TypeScript codegen

* Migrate all operators to genType

* Migrate all sinks to genType

* Migrate sources to genType

* Migrate web to genType

* Delete obsolete .d.ts signature files

* Clean up main folder structure

* Add new main src/wonka.ts entrypoint

* Combine all separate granular files

* Remove fromListener

* Add missing shims

* Move include folder to src

* Convert pipe helper to pipe.ts with overloads

* Fix build output

* Update flow typegeneration

* Fix missing Js.shim.ts types

* Refactor tasks

* Add unwrapStatePlugin to optimise size

Unwraps all `let state` usages across all
operators, since internally this will not
change any functionality while optimising for
output size.

* Unwrap refs using unwrapStatePlugin

Also unwrap all ref types which are output
as objects of the shape: { contents: T }

* Fix forEach types not being generated

* Add full clean script

* Simplify pipe overload typings

* Add initial operator spec tests

* Add test for delay/debounce/throttle using fake timers

* Add additional initial unit tests to all operators

* Collect coverage from non-generated / non-helpers files

* Add spec test for single Start signal

Verify that each operator only sends a single
Start event

* Add spec test for closing operators End/Close

Verify that closing operators send the Close
talkback signal upwards and the End signal
downwards.

* Add sync tests for mergeMap, switchMap & concatMap

* Add stricter ending criteria

Check that Close and End aren't duplicated

* Add test for strict end

Some operators stop forwarding signals when the
source has ended. This is not strictly necessary,
but this test may highlight some other edge cases
and bugs, but it may also become necessary for
sources that aren't well behaved.

* Add additional async sequence test

* Add tests for combine operator

* Add asynchronous tests for switchMap, mergeMap & concatMap

* Add initial tests for Wonka sources

* Add more sources to tests

* Ignore wonka.bs.js/wonka.ts in coverage report

* Add source tests for cold Pull waiting

* Revert changes to Wonka_observable implementation

* Add tests for fromObservable

* Fix genType codegen for Callbags

* Add tests for fromCallbag

* Add tests for cancellation of sources

* Replace publish with subscribe with noop fn

* Add tests for Wonka sinks

* Update package.json and README.md

* Fix coverage and add test for publish

* Remove obsolete TODO comments

* Replace Sail CI with Travis

* Replace babel-jest with custom script

* Test makeSubject after complete has been called

* Add missing tests for interval and fromDomEvent

* Remove obsolete .jest.coverage.json

* Add old TypeScript types for various opaque genTypes

Add old definitions for talkbackT, signalT, observableSubscriptionT,
observableObserverT, observableT, and callbagT.

This will provide more backwards compatibility.

* Update .travis.yml command for codecov