Introduce continuous integration

[kwonoj]

We would like to introduce continuous integration for few purposes. As an initial step, it may need to include

• lint
• build
• test

mostly lint / build should be identical to what current RxJS repo does. For further we'd like to enable bot as well to check commit messages and etcs but that's separate story. (Personally, I'd like to have bot captures screenshot for PR and post it)

[kwonoj]

/cc @ladyleet @feloy

[kwonoj]

think this issue can be closed via #21. Further improvement can be made separately.