Support for <ol> to have line numbers

[iafan]

Would you be interested in accepting iafan@0da6819 as a PR?

This commit introduces AsOrderedListHTML function which, in addition to highlighting the source, wraps each line in <li>..</li>, and then adds <ol>..</ol> global wrapper. The resulting highlighted source code now has line numbers.

Commit comes with full test coverage.

[iafan]

Note that I initially wanted to make as little changes to the code as possible and avoided changing the signature of AsHTML() function, but it might make more sense to use functional parameters here so that API could look like this:

// default backward-compatible call
got, err := AsHTML(input)

// with optional parameter
got, err := AsHTML(input, OrderedList())

[sqs]

Absolutely. Go ahead and submit it. Thanks'

[iafan]

Great. Would you like me to adjust it to the proposed functional API above? Or do you prefer a separate AsOrderedListHTML function as in the current code?

[sqs]

The separate top-level function is fine with me. Whichever one you prefer.

[iafan]

Ok, I went ahead with functional params as this reduces the API surface and is more future-proof in case there will be other options.

[dmitshur]

I believe this issue was resolved in #21 and can be closed, is that right?

[sqs]

Yep, thanks!