Adding support for graphql@0.12.0 and graphql@0.13.0 (#119)

* Adding support for 0.12.0 and 0.13.0, as well as making sure to test all available versions.

* Resolving circular dependency

* Update list of available validators (as of GraphQL 0.13.2) (#121)

* Configure Renovate (#111)

* Update list of available validators (as of GraphQL 0.13.2)

* Switching Node versions

* Moving to `npm@5` to make interop with `tav` easier.

.tav.yml

@@ -0,0 +1,4 @@
+
+graphql:
+  versions: ^0.12.0  || ^0.13.0
+  commands: mocha test/index.js

.travis.yml

@@ -1,7 +1,7 @@
 language: node_js
 node_js:
-  - "5"
-  - "4"
+  - "8"
+  - "6"
 install:
   - npm install
 

README.md

@@ -304,8 +304,7 @@ module.exports = {
 ```
 
 The full list of available validators is:
-  - `ArgumentsOfCorrectType`
-  - `DefaultValuesOfCorrectType`
+  - `ExecutableDefinitions`
   - `FieldsOnCorrectType`
   - `FragmentsOnCompositeTypes`
   - `KnownArgumentNames`
@@ -321,12 +320,16 @@ The full list of available validators is:
   - `PossibleFragmentSpreads`
   - `ProvidedNonNullArguments` (*disabled by default in `relay`*)
   - `ScalarLeafs` (*disabled by default in `relay`*)
+  - `SingleFieldSubscriptions`
   - `UniqueArgumentNames`
+  - `UniqueDirectivesPerLocation`
   - `UniqueFragmentNames`
   - `UniqueInputFieldNames`
   - `UniqueOperationNames`
   - `UniqueVariableNames`
+  - `ValuesOfCorrectType`
   - `VariablesAreInputTypes`
+  - `VariablesDefaultValueAllowed`
   - `VariablesInAllowedPosition`
 
 ### Named Operations Validation Rule
@@ -545,4 +548,4 @@ module.exports = {
     'graphql'
   ]
 }
-```
+```