Add flag for skipping lambda deployment

[bcongdon]

As discussed in #6, it might be useful to have a flag that skips the compilation/deployment step for Lambda invocations.

Pros:

• If you have a really complicated job (code wise), it may be annoying/unnecessary to compile for each invocation

Cons:

• Could pretty easily be a footgun. (i.e. you make code changes that aren't deployed)

This shouldn't be difficult to implement -- just needs a new CLI flag and something in the lambda deployment process that skips compilation/upload under the presence of the flag.