Refactor to cleanup type tests

Closes GH-10.

Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Author: ChristianMurphy

package.json

@@ -17,7 +17,8 @@
   "bugs": "https://github.com/syntax-tree/unist-util-is/issues",
   "author": "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
   "contributors": [
-    "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
+    "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
+    "Christian Murphy <christian.murphy.42@gmail.com>"
   ],
   "files": [
     "index.js",
@@ -28,15 +29,15 @@
   "types": "index.d.ts",
   "dependencies": {},
   "devDependencies": {
+    "@types/mdast": "^3.0.3",
     "browserify": "^16.0.0",
-    "dtslint": "^0.9.0",
+    "dtslint": "^1.0.2",
     "nyc": "^14.0.0",
     "prettier": "^1.0.0",
     "remark-cli": "^7.0.0",
     "remark-preset-wooorm": "^6.0.0",
     "tape": "^4.0.0",
     "tinyify": "^2.0.0",
-    "typescript": "^3.5.3",
     "unified": "^8.3.2",
     "xo": "^0.24.0"
   },

tsconfig.json

@@ -2,10 +2,6 @@
   "compilerOptions": {
     "lib": ["es2015"],
     "strict": true,
-    "noImplicitAny": true,
-    "noImplicitThis": true,
-    "strictNullChecks": true,
-    "strictFunctionTypes": true,
     "baseUrl": ".",
     "paths": {
       "unist-util-is": ["index.d.ts"],

tslint.json

@@ -1,15 +1,7 @@
 {
   "extends": "dtslint/dtslint.json",
   "rules": {
-    "callable-types": false,
-    "max-line-length": false,
-    "no-redundant-jsdoc": false,
-    "no-void-expression": false,
-    "only-arrow-functions": false,
     "semicolon": false,
-    "unified-signatures": false,
-    "whitespace": false,
-    "interface-over-type-literal": false,
-    "no-unnecessary-generics": false
+    "whitespace": false
   }
 }

unist-util-is-test.ts

@@ -1,15 +1,10 @@
 import {Node, Parent} from 'unist'
+import {Heading} from 'mdast'
 import unified = require('unified')
 import is = require('unist-util-is')
 import convert = require('unist-util-is/convert')
 
 /*=== setup ===*/
-interface Heading extends Parent {
-  type: 'heading'
-  depth: number
-  children: Node[]
-}
-
 interface Element extends Parent {
   type: 'element'
   tagName: string