Create BLA Bandit

[norases]

Create a simple endpoint bandits/bla for BLA (under moe/bandits).

REST endpoint
url/bandit/bla

Request:
{
"subtype": "BLA",
"historical_info": {
"arms_sampled": {
"arm1": {"win": 20, "loss": 0, "total": 25},
"arm2": {"win": 20, "loss": 0, "total": 30},
"arm3": {"win": 0, "loss": 0, "total": 0},
},
},
}

Response:
{
"arm_allocations": {
"arm1": 0.0,
"arm2": 0.0,
"arm3": 1.0,
}
"winner": "arm3",
}