Prepare for creating wasm builds

[Senyoret1]

Changes:

• Now it is possible to compile a wasm version of the library. The code was created for Go v1.12.x. it does not work with Go v1.11.x and will probably not work with Go v1.13.x, as the wasm compiler is still getting breaking changes.

• A version of the cipher test suite for the wasm version was added.

• The file wasm_exec.js is https://github.com/golang/go/blob/master/misc/wasm/wasm_exec.js for Go v1.12.

• The possibility of using GopherJS is still active, just in case. However, the wasm version is much faster, so the GopherJS version should be removed if we do not find problems.

I will check this PR again latter, just in case.

[Senyoret1]

I checked the PR again and found nothing relevant, I just changed parts of the documentation and added comments to the Go file. I also made changes to the Travis config, and deactivated the checks for the GopherJS version in Travis (as those need Go v1.10 and the wasm build needs Go v1.12). However, it is still necessary to make changes to the Go linters config.

[Senyoret1]

With the lastest commit the wasm test does not only includes the cipher test suite (which was translated from Go to TypeScript), but also compiles the test files found in src/cipher/sec256k1-go/ and src/cipher/sec256k1-go/secp256k1-go2/ to wasm files and runs them (this time directly compiled from Go to wasm, not translated to TypeScript).

Currently the Go wasm builds don’t return the exit code to the calling js code without making modifications, but as a warning is shown in the console, the tests code detect that warning for failing.

[gz-c]

Merge conflicts

[Senyoret1]

In the last 2 commits, due to #34, the following changes were made:

• The conflects were solved.

• The code related to the wasm version was updated.

• The code for running a wasm version of the test on /vendor/github.com/skycoin/skycoin/src/cipher/secp256k1-go and /vendor/github.com/skycoin/skycoin/src/cipher/secp256k1-go/secp256k1-go2 was rewritten, as after updating the Skycoin cipher library the previous method stopped working due to timeouts.

• The tests on the vendor folder were updated.

• Small changes to the readme.

[Senyoret1]

@gz-c The last 2 commits solve the remaining problems with the linter and the tests. However, for some reason Travis made this build: https://travis-ci.com/skycoin/skycoin-lite/builds/119038575 but did not report the result here.

[Senyoret1]

Nevermind, Travis just taked a lot of time before reporting the result on Github

[gz-c]

I believe this defaults to true, you may want to be explicit go-tests = false and leave a comment why (for the wasm tests)

[Senyoret1]

Adding go-tests = false makes dep ensure say root prune options must be omitted instead of being set to false

[gz-c]

Can we run these tests for cipher/ as well?

[Senyoret1]

Yes, no problem. Done in the lastest commit

[Senyoret1]

The last commit includes the following changes:

• Now make test-suite-ts-wasm also runs the test found inside /github.com/skycoin/skycoin/src/cipher.

• The code on cipher-wasm-internal.js was modified to make it easier to run additional Go tests.

• The package github.com/stretchr/testify/require was added to the required list in Gopkg.toml, as it is needed for the new tests, and the vendor folder was updated.