fix: examples with servers, tests and travis config

[MartinKavik]

Well, little bit bigger PR, but it mostly changes only examples and there are no api / breaking changes.
(It should be my last too big PR - build and test pipeline should be working now for every examples and CI.)

Summary of changes:

A) Rewritten server_integration example.
B) Rewritten websocket example.
C) Fixed tests.
D) Updated + created Makefile.tomls.
E) Updated + created README.mds.
F) Rewritten .travis.yml.
G) Deleted useless files.
H) Added body() into util.rs.

---

A) Rewritten server_integration example.

• Old example was using Rocket, so it required nightly Rust - problematic compilation
• Old example didn't show how to scale and manage project with workspaces
• New example uses Actix and workspace - it should be a nice example of modern Rust application with Wasm, actors and stable Rust
• Actix has websockets out of the box and with workspace it will be easy to add another websocket example in the future (WebSocket support & example #8)

B) Rewritten websocket example.

• I think that old example was too complex - it was more like server-integration with websockets and some low-level operations
• New example uses ws-rs (there are now 46 lines of code instead of 169 with the same logic in server.rs) - it will be useful when we will be testing new websocket crate / functions in the future (WebSocket support & example #8)
• I've also refactored client, because there were compilation problems and I tried to make it more readable.

C) Fixed tests.

• I've just commented out a few lines, added arguments to functions and write some comments so tests pass now. See changes in /src/vdom.rs and /src/dom_types.rs - probably related to Hooking into lifecycle events for cleanup #82 or Recommended way of triggering model events from outside of normal flow. #85

D) Updated + created Makefile.tomls.

• Each example can be started from Seed's root (cargo make start counter) or from own root (cargo make start).
• Main (root) Makefile.toml refactored, modified and added test tasks.
• Fixed bugs that fail CI pipeline.

E) Updated + created README.mds.

• Each example has own README. Old readmes updated.
• Main (root) readme
  • Added badges for better "marketing" and as quick links to travis and cargo-make
  • Chapter Running included examples updated.
  • Added --force so people has current cargo-make and it doesn't fail when they use it in CI

F) Rewritten .travis.yml.

• It uses cargo-make now
• Switched to stable from nightly
• Added basic cache configuration
• Added chrome
• It is a little bit slow (mainly on mac) due to unnecessary recompilations / bad caching and downloading - I've added useful links at the end of the file for future work => I think it makes sense to optimize it when the windows environment will be stable and some new features in cargo will be published ; https://travis-ci.org/MartinKavik/seed

G) Deleted useless files.

• build.ps1, build.sh, serve.py ...

H) Added body() into util.rs.

• I've had to mount App into something in DOM during tests.

[David-OConnor]

Excellent PR! Solid changes/fixes all around. Your cargo make system (this PR and previous) is a night-and-day improvement to usability/getting started.