Add setting for max cluster size

[beedub]

I tried to regenerate the templates as well, but got:

$ make -C api templates ; make fixtures
go-bindata -nometadata -pkg=models -prefix=models -o=models/templates.go models/templates/...
go-bindata -nometadata -pkg=aws -prefix=provider/aws -o=provider/aws/templates.go provider/aws/templates/...
go install github.com/convox/rack/api/cmd/fixture
rm api/models/fixtures/*.json
make -C api/models/fixtures
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture balancer_labels.yml > balancer_labels.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture command_exec_form.yml > command_exec_form.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture command_string_form.yml > command_string_form.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture complex_environment.yml > complex_environment.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture custom_health.yml > custom_health.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture environment_map.yml > environment_map.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture multi_balancer.yml > multi_balancer.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture web_external_internal.yml > web_external_internal.json
env AWS_REGION=us-test-2 PROVIDER=test RACK=convox-test fixture web_postgis.yml > web_postgis.json
ERROR: web links to service: postgres which does not expose any ports
make[1]: *** [web_postgis.json] Error 1
make: *** [fixtures] Error 2

[codecov-io]

Current coverage is 16.67% (diff: 100%)

Merging #1036 into master will not change coverage

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  Misses         9539       9539          
  Partials        123        123          

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[ddollar]

Is there any reason to not just set this to a really big number in the first place?

[beedub]

That was my first thought, but I thought people might want to have a max safeguard and not accidentally start 1000 servers? Either way is fine for me for now

[ddollar]

I think we can let EC2 limit take care of the safeguards for now and just make this a really big number.

[beedub]

set statically to 1000 @ddollar