_3llo: init at 0.3.0

Simple CLI client for `trello.com`. It can be used like this:

```
$ export TRELLO_USER=your_username
$ export TRELLO_KEY=your_key
$ export TRELLO_TOKEN=your_token
$ ./result/bin/3llo
```

I didn't create a module for this as I don't think that those secrets
should live in the Nix store. Ideally `3llo` can be used from a script
which retrieves secrets from some kind of password store like this:

```
export TRELLO_KEY=$(pass show trello/key)
export TRELLO_TOKEN=$(pass show trello/token)
3llo $@
```

pkgs/tools/misc/3llo/default.nix

@@ -0,0 +1,31 @@
+{ lib, ruby, bundlerApp, fetchpatch }:
+
+bundlerApp {
+  pname = "3llo";
+
+  gemfile = ./Gemfile;
+  lockfile = ./Gemfile.lock;
+
+  gemset = lib.recursiveUpdate (import ./gemset.nix) ({
+    "3llo" = {
+      dontBuild = false;
+      patches = [
+        (fetchpatch {
+          url = https://github.com/qcam/3llo/commit/7667c67fdc975bac315da027a3c69f49e7c06a2e.patch;
+          sha256 = "0ahp19igj77x23b2j9zk3znlmm7q7nija7mjgsmgqkgfbz2r1y7v";
+        })
+      ];
+    };
+  });
+
+  inherit ruby;
+
+  exes = [ "3llo" ];
+
+  meta = with lib; {
+    description = "Trello interactive CLI on terminal";
+    license = licenses.mit;
+    homepage = https://github.com/qcam/3llo;
+    maintainers = with maintainers; [ ma27 ];
+  };
+}