Avoids packaging TypeScript sources to avoid .d.ts conflicts

[zsims]

This is part of fixing #69.

Per microsoft/TypeScript#7432 the TypeScript compiler will attempt to
compile the TypeScript sources if they're found. This is because definitions (.d.ts) do not take
precedence over source files.

New package contents:

$ npm pack
$ tar -tf pact-foundation-pact-node-6.7.2.tgz --wildcards 'package/src/*.ts'
package/src/publisher.d.ts
package/src/index.d.ts
package/src/pact.d.ts
package/src/pact.spec.d.ts
package/src/index.spec.d.ts
package/src/broker.spec.d.ts
package/src/publisher.spec.d.ts
package/src/server.d.ts
package/src/logger.d.ts
package/src/server.spec.d.ts
package/src/broker.d.ts
package/src/service.d.ts
package/src/stub.d.ts
package/src/pact-util.d.ts
package/src/stub.spec.d.ts
package/src/verifier.d.ts
package/src/verifier.spec.d.ts
package/src/pact-util.spec.d.ts

[mboudreau]

Yep, looks good. Deploying a new version without the ts files, 6.7.3.