Handle .x version syntax with latest release (#13)

* get latest release for .x syntax version

* added nock as dev dependency

* added test for .x syntax

* updated readme

* updated http client name

* use rest client for getting available versions

* more .x handling

* move nock to setup and teardown

README.md

@@ -30,7 +30,7 @@ jobs:
     runs-on: ubuntu-16.04
     strategy:
       matrix:
-        go: [ '1.8', '1.9.3', '1.10' ]
+        go: [ '1.8', '1.9.3', '1.10.x' ]
     name: Go ${{ matrix.go }} sample
     steps:
       - uses: actions/checkout@master