No license specified

[jhorsley]

I couldn't see what license the project is operating under. d3.js is BSD is gwt-d3 the same given it's just a wrapper around d3?

(This is a duplicate of anthonime/gwt-d3#45 but for the correct project now.)

[anthonime]

The license is BSD. The license file has been added and the source files have now the appropriate license header.
Moreover, the continuous build process is configured to break the build if some sources don't include the license header.