switched nedb to nedb-promises (#37)

* breaking change: switched to nedb-promises
* Linting
* some dev dependencies
* more tests
* updated package version
* bug fixing
* changed isNaN to isString
* (fix) args[0]

.eslintrc

@@ -0,0 +1,90 @@
+{
+    "parserOptions": {
+        "ecmaVersion": 10,
+        "sourceType": "script",
+        "ecmaFeatures": {
+            "jsx": true
+        }
+    },
+    "rules": {
+        "constructor-super": 2,
+        "for-direction": 2,
+        "getter-return": 2,
+        "no-async-promise-executor": 2,
+        "no-case-declarations": 2,
+        "no-class-assign": 2,
+        "no-compare-neg-zero": 2,
+        "no-cond-assign": 2,
+        "no-const-assign": 2,
+        "no-constant-condition": 2,
+        "no-control-regex": 2,
+        "no-debugger": 2,
+        "no-delete-var": 2,
+        "no-dupe-args": 2,
+        "no-dupe-class-members": 2,
+        "no-dupe-else-if": 2,
+        "no-dupe-keys": 2,
+        "no-duplicate-case": 2,
+        "no-empty": 2,
+        "no-empty-character-class": 2,
+        "no-empty-pattern": 2,
+        "no-ex-assign": 2,
+        "no-extra-boolean-cast": 2,
+        "no-extra-semi": 2,
+        "no-fallthrough": 2,
+        "no-func-assign": 2,
+        "no-global-assign": 2,
+        "no-import-assign": 2,
+        "no-inner-declarations": 2,
+        "no-invalid-regexp": 2,
+        "no-irregular-whitespace": 2,
+        "no-misleading-character-class": 2,
+        "no-mixed-spaces-and-tabs": 2,
+        "no-new-symbol": 2,
+        "no-obj-calls": 2,
+        "no-octal": 2,
+        "no-prototype-builtins": 0,
+        "no-redeclare": 2,
+        "no-regex-spaces": 2,
+        "no-self-assign": 2,
+        "no-setter-return": 2,
+        "no-shadow-restricted-names": 2,
+        "no-sparse-arrays": 2,
+        "no-this-before-super": 2,
+        "no-undef": 2,
+        "no-unexpected-multiline": 2,
+        "no-unreachable": 2,
+        "no-unsafe-finally": 2,
+        "no-unsafe-negation": 2,
+        "no-unused-labels": 2,
+        "no-unused-vars": 2,
+        "no-useless-catch": 2,
+        "no-useless-escape": 2,
+        "no-with": 2,
+        "require-yield": 2,
+        "use-isnan": 2,
+        "valid-typeof": 2,
+        "no-underscore-dangle": 0,
+        "spaced-comment": 0,
+        "no-console": 0,
+        "no-unneeded-ternary": 0,
+        "object-shorthand": 0,
+        "no-useless-rename": 0
+    },
+    "env": {
+        "node": true,
+        "jest": true,
+        "commonjs": true,
+        "es2017": true
+    },
+    "plugins": [
+        "prettier"
+    ],
+    "extends": [
+        "airbnb",
+        "prettier"
+    ],
+    "settings": {
+        "import/resolver": "module-alias"
+    }
+}