Support custom ipc paths

[njgheorghita]

Ready for review after #2 is merged

• Fixes Extract client logic from cli module into new jsonrpc module #7 (extract jsonrpc logic into separate module)
• Fixes Allow specifying the IPC location #5 (support custom ipc paths)
• Updated DEFAULT_HTTP_PORT and DEFAULT_IPC_PATH to be constants

[carver]

Would be nice to print the IPC path here.

[carver]

So this approach no longer seems acceptable with a configurable IPC path (just dropping whatever file is found there and replacing it).

The simple answer is that we should just panic instead of trying to remove the file and reattempting. But then to solve the original problem: I think that we were leaking the file on shutdown sometimes. (Maybe anytime there's a panic?)

So the next step is to make sure that the IPC file gets removed when trin shuts down, even after a panic. (Although, it's probably worth verifying the theory. All I really know is that sometimes it used to happen that I had a pre-existing file on startup, and it was annoying. Not sure where it came from).

[njgheorghita]

I updated the code to add some handlers that will clean up the ipc file upon ctrl+c shutdown and all panics. It works as expected locally, but could use some integration tests to make sure the cleanup happens as expected. I'm leaning towards saving those for a larger integration test pr coming soon^tm.

[carver]

I took the liberty of rebasing

[carver]

Reminder to rebase on master to get CI tests

[njgheorghita]

@carver ping for another 👀. I updated the settings in circle ci to "Build forked pull requests" and "Pass secrets to builds from forked pull requests" - both of which are necessary to get ci working here. FYI re: passing secrets -> "passing secrets to builds from forked pull requests can cause security vulnerabilities"- which seems fine since we're using a dummy infura key for now. Even when we use a real infura key for integration testing, imo it doesn't warrant a more secure setup, but it's something to keep in mind.