Removed Travis and Greetings workflows (#415)

* removed greetings workflow, and travis

* Update the build status badge to point to Github Actions

.github/workflows/greetings.yml

@@ -1,14 +0,0 @@
-name: Greetings
-
-on: [pull_request, issues]
-
-jobs:
-  greeting:
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/first-interaction@v1
-      with:
-        repo-token: ${{ secrets.GITHUB_TOKEN }}
-        issue-message: "Hola! @${{ github.actor }} 🥳 , You've just created an Issue!🌟 Thanks for making the Project Better"
-        pr-message: 'Submitted a PR already ?? @${{ github.actor }} . Sit tight until one of our amazing maintainers review it. Make sure you read the contributing guide'
-