Adding additional essays

[shirishp]

Hi.

There were additional 68 essays available on the http://programmer.97things.oreilly.com website, which are missing from this Gitbook version.

I had published them on Leanpub here - https://leanpub.com/97-Things-Every-Programmer-Should-Know-Extended

I would like to add those to this repository (only English version). If you are open for it, I can send a PR.

[Semigradsky]

Feel free to send PR!

[shirishp]

Thanks. Working on it.

Quick question: Do you prefer to continue directory names like thing_98, thing_99... or we should create a parallel directory structure as extended_01, extended_02...?

[Semigradsky]

I think extended_xx would be better

[shirishp]

@Semigradsky Can you please review the changes in this repo? https://github.com/shirishp/97-things-every-programmer-should-know/tree/master/en

I can send a PR if the changes look good.