Add go install compatibility

[najose]

• Move away from depending on Go's test mechanism to compile binaries and instead use regular package namespace and file names so that it can be compiled using go build
• Restructure source directory to make the package installable using go install
• Update package name from schrodinger.com/infra-tester to github.com/schrodinger/infra-tester
• Update go dependency versions
• Update docs

Closes #21 and #22

[fwolfheimer]

LGTM