tests: use bats for integration tests

Converted the CLI tests to using bats to get started

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

tests/helpers.bash

@@ -0,0 +1,12 @@
+common_setup() {
+    load 'node_modules/bats-support/load'
+    load 'node_modules/bats-assert/load'
+
+    TESTDIR="$( cd "$( dirname "$BATS_TEST_FILENAME" )" >/dev/null 2>&1 && pwd )"
+
+    DAGGER="${DAGGER_BINARY:-$TESTDIR/../cmd/dagger/dagger}"
+    export DAGGER
+
+    DAGGER_STORE="$(mktemp -d -t dagger-store-XXXXXX)"
+    export DAGGER_STORE
+}