Remove process spawn, old TypeScript versions

[blakeembrey]

• Fixes issues with CLI arguments and environment variables
• Uses TypeScript throughout to parse tsconfig.json file
• Removes support for pre-2.0 APIs
• Removes support for advanced node.js CLI flags (use node -r ts-node/register instead)
• BREAKING --project must be full path (for now)

[coveralls]

Coverage decreased (-0.3%) to 77.121% when pulling 68687e1 on remove-subprocess into d5a941c on master.

[coveralls]

Coverage decreased (-0.3%) to 77.121% when pulling 68687e1 on remove-subprocess into d5a941c on master.