Add Travis config

[mre]

Would be great to build the project on every new commit / pull request.
For that, we could add a Travis configuration.

[schalkneethling]

@mre Hey there, I would like to take this one. I am guessing that you want to run the default Rust build script on PR/commit i.e. cargo build

Is there a specific version of Rust you want to target? Perhaps simply release?
Do you also want to run cargo test?

[mre]

Hey @schalkneethling,
yeah I think a setup like this would be a good start: https://github.com/mre/mos6502/pull/4/files
This runs cargo build and cargo test. You might also want to add a badge to the README.md if you can. Once we got this up and running, we might wanna think about adding support for wasm-pack to Travis, as described in #2.

[schalkneethling]

Sounds good @mre - on it.

[mre]

Fixed by @schalkneethling in #6. 🎉