remove Local variants of QVMCompiler and BenchmarkConnection

[ecpeterson]

With the advent of an RPCQ-enabled SDK, there's no need to distinguish between local/remote communication protocols. This PR removes the HTTP-based connection classes for QVMCompiler and BenchmarkConnection and modifies the get_... calls to return the appropriate RPCQ variants all the time.

Also:

• Add timeout fields to QVMCompiler and BenchmarkConnection for testing purposes.
• Minor other tweaks to get the tests to pass.

Don't merge this 'til the RPCQ-enabled version of quilc is available for download.

[mpharrigan]

good to go, pending availability of new quilc binary

[karalekas]

one question: do we want to deprecate this code instead of deleting it? are we concerned about people slowly switching over to the rpcq version of quilc?

[ecpeterson]

It's a thought, but I would view it more as a polite thing to do than something required by good practices. Having to update a dependent piece of Rigetti software when you update your pyQuil, which ultimately both have the same functionality in this regard, does not strike me as being too pushy.

[ecpeterson]

Note to self: http://docs.rigetti.com/en/stable/start.html#server needs to get updated before this is reconsidered.

[ecpeterson]

Semaphore mysteriously timed out on the RB sequence generation test, but (after rerunning it a few times with different configurations on my local machine & not being able to reproduce the error) I reran the semaphore script and it passed through. A little concerning? Or maybe it's fine!