'Release mode' builds

In bazel instead of passing --release you need to set the compilation-mode, which is a command-line option you can set that affects both the rust and c++ compilation in our example repo. When you run bazel build or bazel run you'll want to use this flag to get compiler optimizations turned on.

#Compiles everything with optimization enabled
bazel build -c opt //...

#Runs out example CLI from a build with optimization enabled
bazel run -c opt //src/summation:executable