Add sample data and a Makefile target to expand it

Use `make sample-data` to generate a ~500MB test input file.
Merge pull request #8 from mreid-moz/sample-data

Add sample data and a Makefile target to expand it
Add a go target and a few other things

Add a Makefile target to build and run the go benchmark
Default to using the generated sample data
Add a SPIDERMONKEY parameter for the location of `js`
Merge pull request #10 from mreid-moz/makefile-changes

Add a go target and a few other things
A couple more Makefile tweaks

Automatically download rapidjson for making the c++ version
Remove some awkwardness with the `go` target
Add dependency from `cxx` to `json` so you can run everything in one step
Merge pull request #11 from mreid-moz/more-makefile-changes

A couple more Makefile tweaks