WIP: Update microbenchmarks for 0.3 release

Closes #131

Unfortunately, remaking the Gadfly plot has been complicated by the near-complete obsolescence of the code in the benchmarks notebook. It would be great if someone else could look into updating the figure.

cc: @dcjones @StefanKarpinski 

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Update: Issues with microbenchmarks in other languages ought to be addressed:

- [x] C constant folding JuliaLang/julia#4821
- [x] Fortran constant folding JuliaLang/julia#4821 and possibly other compiler optimizations
- [x] Java JuliaLang/julia#6319
- [x] Octave JuliaLang/julia#6791
- [x] R JuliaLang/julia#6804