Move @types/readable-stream to devDependencies Fixes #145

[guyellis]

This should fix an upstream dependency issue that Tedious is having with TypeScript and the location of this dependency.

[rvagg]

Error: node_modules/@types/readable-stream/index.d.ts(419,11): error TS2420: Class 'Readable' incorrectly implements interface 'ReadableStream'.
  Types of property 'wrap' are incompatible.
    Type '(oldStream: Readable) => this' is not assignable to type '(oldStream: ReadableStream) => this'.
      Types of parameters 'oldStream' and 'oldStream' are incompatible.
        Type 'ReadableStream' is not assignable to type 'Readable'.
          Type 'ReadableStream' is missing the following properties from type 'Readable': readableAborted, readableDidRead, readableEncoding, readableEnded, and 28 more.