add optimization flags

Test runs go from 23s with -O0 to 3.3s with -Ofast. wow.

Note that adding optimizations to yaml-cpp makes a *big* difference to
spin up time, which is significant (it takes ~seconds to load five or
six v-gene files)
Merge commit '48834563fe6ee1aa2c4a710eb1f6ad22b4d06fa4'