Update docs links
Update more links
Remove target=_blank
Added The Little Elixir & OTP Guidebook link
Use a smaller image for the book cover.
Merge pull request #258 from benjamintanweihao/patch-2

Added The Little Elixir & OTP Guidebook link
Translate into japanese(1 Interactive Elixir)
Translate into japanese(2 Basic types)
Translate into japanese(3 Basic operators)
Translate into japanese(4 Pattern matching)
Translate into japanese(5 case, cond and if)
Translate into japanese(6 Binaries, strings and char lists)
Translate into japanese(7 Keywords, maps and dicts)
Translate into japanese(8 Modules)
Translate into japanese(9 Recursion)
Translate into japanese(10 Enumerables and Streams)
Translate into japanese(11 Processes)
Translate into japanese(12 IO)