Update NPM name to be organization scoped

[rockacola]

Description

Migrate NPM package name from neo-js-blockchain to @cityofzion/neo-js joining the organisation scope.

Types of changes:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[rockacola]

@lllwvlvwlll , when approved, can I get you to:

• perform npm publish as a new, appropriate package version.
• apply deprecation notice for all versions below this, informing existing users that we have moved the package to a new namespace.

Thanks.

[rockacola]

Direct update onto master branch, as noted in #109