Updated apache license to remove Packagist error

[cykolln]

• updated to apache license value in composer.json from "Apache2" to "Apache-2.0" to address the Packagist error:

License "Apache2" is not a valid SPDX license identifier, see https://spdx.org/licenses/ if you use an open license. If the software is closed-source, you may use "proprietary" as license.

[remstone7]

@smoucka i think we do because it's done all on releases, we already did a release so if we merge this is just in the dev-master not in a specific released version. Most people download the version from composer (it does it by default) its not common to do a require dev-master for a package