1.2.0 - Maintenance Release

This is a maintenance release after a longer period with no releases. See PR #81 for implementation details.

Changes

• scrypt to scrypt-js for a pure js implementation (simplifies some code)
• keccak from 1.4.0 to 3.1.0 for node 12 and n-api support
• secp256k1 from 3.5.0 to 4.0.2 for node 12 and n-api support
• travis ci node versions from [4, 5, 6, 7, 8] to [8, 10, 12, 13, 14]
• uglify-js to terser (build was having some trouble with es6 in node_modules)
• browserify from 16.2.2 to 16.5.2 for misc. bug fixes and upgrades.