WIP: Add branch prediction benchmarks

[stefreak]

How many times in one second can you sort a 500-element array:

• that is already sorted
• that is sorted randomly

Branches can make CPUs slow, if they fail to predict their outcome.

The branches in this example are part of the sorting algorithm: "Is element n bigger than n+1? If yes, change the order!"

[stefreak]

@kamalmarhubi @jvns do you think it's worth it investing the time to finish this and add it to the curriculum?

Benchmark results:

----> benchmarks/branch.py
   rounded iterations: 100000
   exact iterations:   103595
   final time taken:   1.05427289009
----> benchmarks/branch_mispredictions.py
   rounded iterations: 10000
   exact iterations:   10512
   final time taken:   1.13148808479

I believe run_benchmarks.py adds the results to the json file, but I get following error in the end:

----> benchmarks/sum.c
Traceback (most recent call last):
  File "./run_benchmarks.py", line 91, in <module>
    for result in run_benchmarks(all_benchmarks):
  File "./run_benchmarks.py", line 66, in run_benchmarks
    yield benchmark(source)
  File "./run_benchmarks.py", line 34, in benchmark
    iters = int(math.ceil(iters))
OverflowError: cannot convert float infinity to integer