Add flag to indicate project root

[codehakase]

Summary

Add flags to indicate the project root and entry point file to run.

Problem Definition

Currently, the rld command only watches for changes on the specified file (os.Args[1]) and not the entire project.

Proposal

Add two flags root and entrypoint to indicate the project's root and the file to run the program with:

$ rld -r ~/Dev/proj -e cmd/proj/main.go

[oneEyedSunday]

So this will mean if a project root is specified, rld should watch all files in the root folder? and run the file specified in the entrypoint?