This commit creates a new probe_and_replicate.txt interactive test. The
test creates a complete Raft log configuration and demonstrates how a
leader probes and replicates to each of its followers. The log
configuration constructed is identical to the one present in Figure 7 of
the raft paper (https://raft.github.io/raft.pdf), which looks like:
```
1 2 3 4 5 6 7 8 9 10 11 12
n1: [1][1][1][4][4][5][5][6][6][6]
n2: [1][1][1][4][4][5][5][6][6]
n3: [1][1][1][4]
n4: [1][1][1][4][4][5][5][6][6][6][6]
n5: [1][1][1][4][4][5][5][6][7][7][7][7]
n6: [1][1][1][4][4][4][4]
n7: [1][1][1][2][2][2][3][3][3][3][3]
```
Once in this state, we then elect node 1 as the leader and stabilize the
entire raft group. This demonstrates how a newly elected leader probes
for matching indexes, overwrites conflicting entries, and catches up all
followers.
This will be useful to demonstrate the impact of more efficient probing
behavior.
