Add support for a title, docstrings-tags and expose private methods

[pietervdvn]

Hi Danr,

I'm quite fond of doctesting, but found a few missing features that would improve my life. So, I gave it a go to improve doctest-ts.

The first issue is that, when testing a private method, the generated doctest would not compile as this private method is not visible in the describe block (at least not in mocha/jest). The function exposePrivates will rewrite a piece of code and replace every private-keyword with a public-keyword and convert this into a script, which is then used in the .doctest.ts-testfile.

A second issue was that, as soon as a tag is used in a docstring, doctest-ts would ignore tests:

/**
* This method does XYZ
* @example xyz(42)
*
* xyz(42) // => 1234
*/
function xyz(a) {
   ...
} 

The test here would be ignored. This is fixed by also checking node.jsDocs.tags in the Comments-function (L56 - L61)

At last, a small quality-of-life improvement: when the first line of a valid docstring is a comment, this is treated as the name of the test, e.g.

/**
* 
* // should equal 1234
* xyz(42) // => 1234
*
* // should equal "abc"
* xyz("abc") // => "abc"
*/
function xyz(a) {
   ...
} 

will result in

describe("xyz", () => {
  it("should equal 42", () => {...})
  it("should equal \"abc\"", () => {...})
})

I've also taken the freedom to update the version number and would be very happy with a quick deploy on NPM. However, if you are unwilling to maintain this library, I will deploy a new version myself.

Kind regards,
Pieter

[pietervdvn]

It seemed like this function is not used, so I removed

[pietervdvn]

detect a name, if any