update dependencies, add dependabot (#70)

* update dependencies
* add some status badges
    crates.io
    testing status
    dependency status
* add cargo-audit ci
* add dependabot for cargo and github actions updates

.github/workflows/cargo-audit.yml

@@ -0,0 +1,18 @@
+name: Cargo Audit Scanning
+on:
+  push:
+    paths:
+      - "**/Cargo.toml"
+      - "**/Cargo.lock"
+  schedule:
+    - cron: "0 14 * * *" # 14:00 UTC
+permissions:
+  repository-projects: read
+jobs:
+  cargo-audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/audit-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}