Support windows (it's pretty easy)

[infa-mpaetzol]

To support windows :

In server.py just change a few lines:
def index():
# we need terraform, graphviz, and an init-ed terraform project.
if not which('terraform') or not which('dot'):
if not which('terraform.exe') or not which('dot.exe'):
return render_template('error.html')
if not os.path.exists('.terraform'):
return render_template('error.html')