This updates the `release.nix` to now correctly run the test suite. You can
now build and test `grpc-haskell` by running:
```
$ nix-build -A grpc-haskell release.nix
```
... and `nix-shell` has been updated, too, so that you can do `cabal`
development inside of a `nix-shell` by running:
```
$ nix-shell -A grpc-haskell.env release.nix
```
For people who prefer to use `stack` you can still just build the `grpc`
library by running:
```
$ nix-build -A grpc release.nix
```
... then pass that library as input to `stack`
* update channel arg names, add compression level arg support, add compression level arg test
* switch to temp test demonstrating bug in grpc 0.15.0
* memset op array to 0
* switch examples back
* Switch to newer `grpc` and enable tests in `release.nix`
* Split out `simple-server` test into separate shell script
* Fix bash invocation
* Add intermediate `./default-tests.nix` build
* Add `tests.patch` to version control
* Split `python` command into separate script
* Provide `python` via `nix`
