version.h missing for generating amalgamated source

[Ni2c2k]

The amalgamated source can't be generated after just cloning repository because there is no include/json/version.h file. But Readme.md says "The amalgamated source can be generated at any time..."

[cdunn2001]

Oh, I was thinking we need a Travis test for building amalgamated source.

version.h is generated, so it cannot be in the repository. We need a way to cause cmake to build it even for the amalgamated-source rule. Any ideas?

[cdunn2001]

#14 fixed this.