{WIP} Implements highlighting

[danmcclain]

WIP DO NOT MERGE

At the end of the filename or language add {1,2,-4,+5},
+ signifies that the line should be marked as added
- signifies that the line should be marked as removed
line numbers are otherwise highlighted

Does not currently handle ranges

Also updates colors in code blocks, fixing contrast

Closes #77

[trek]

I'm 👎 on re-parsing the HTML with Nokogiri after generation. A quick check shows CodeRay already has a way to highlight lines

I'm OK to merge this if you can commit to investigating a better way to handle this sometime this week:

Possible solutions are one or more of:

• see if CodeRay highlighting already supports what we need (highlights of many types).
• fork CodeRay and add this, open a PR on CodeRay referencing this issue, open a PR here pointing at your fork.
• figuring out how to write and use a custom encoder for CodeRay.

[danmcclain]

@trek Makes sense. Let me investigate a little bit later today.

One thing to note: this repo already is using a Coderay fork: https://github.com/emberjs/guides/blob/master/Gemfile#L7

[danmcclain]

Will likely implement this as a custom encoder, using the HTML encoder as a base. Will report later how that is going

[trek]

One thing to note: this repo already is using a Coderay fork:

Can you also follow up on that? I'm assuming this is just because we needed to add a language to mainline CodeRay and never changed back.

[danmcclain]

@trek Coderay lacks handlebars (@dgeb's PR) support. If I use mainline:

[trek]

cc @dgeb: we really need to get that back to mainline.

[trek]

Will report later how that is going

Is this later enough? :D

[danmcclain]

@trek Been sidetracked with an Ember-IE8 breakage. I should have some time this weekend to wrap this up. I have started a custom encoder, should be fine to implement what I need to make this happen. Sorry about the delay

[trek]

OK. going to merge this now, trust that you'll circle back with a smoother solution.

[trek]

Actually, belay that. Let's just wait until it's all done.