Add exec (#10)

* Add exec

* Fix linux tests

* unnecessary dependency

* Dont prefix ExecOptions with I

* Consistency nits

* Respond to feedback

* Add toolrunner explanatory quote

* Format

package-lock.json

@@ -0,0 +1,12 @@
+{
+  "name": "@actions/exec",
+  "version": "1.0.0",
+  "lockfileVersion": 1,
+  "requires": true,
+  "dependencies": {
+    "@actions/io": {
+      "version": "1.0.0",
+      "dev": true
+    }
+  }
+}