Refactor tsconfig (axross#138)

Author: Kohei Asai

Diff for: tsconfig.json

@@ -1,19 +1,12 @@
 {
   "compilerOptions": {
     "lib": ["esnext"],
-    "downlevelIteration": true /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */,
     "strict": true,
-    "noImplicitAny": true,
-    "strictNullChecks": true,
-    "strictFunctionTypes": true,
-    "strictBindCallApply": true,
-    "strictPropertyInitialization": true,
-    "noImplicitThis": true,
-    "alwaysStrict": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "noImplicitReturns": true,
     "noFallthroughCasesInSwitch": true,
+    "downlevelIteration": true,
     "plugins": [{ "name": "typescript-deno-plugin" }]
   }
 }