latex display: unclear which qubits control which gates when multiple controlled gates rendered in same column

[adamglos92]

Pre-Report Checklist

• [x] I am running the latest versions of pyQuil and the Forest SDK
• [x] I checked to make sure that this bug has not already been reported

The display function produce incorrect output, it is easy to confuse them with Toffoli gates,

from pyquil import Program
from pyquil.gates import X
from pyquil.latex import display

p  = Program()
p += X(2).controlled(0)
p += X(3).controlled(1)
display(p)

[appleby]

This is good feedback @adamglos92, thanks for reporting it.