Yohei Yukawa 1c8121087e Rename doc/ to docs/ ...

This CL renames doc to docs/ on GitHub, just in case in future we want
to expose web pages on GitHub Pages [1].

 [1]: https://github.com/blog/2228-simpler-github-pages-publishing

BUG=
TEST=
REF_BUG=
REF_CL=130706872
REF_TIME=2016-08-18T18:22:05-07:00
REF_TIME_RAW=1471569725 -0700

2016-08-18 18:22:05 -07:00

..

data_protection.md

…

input_scope.md

…

mozc_ipc.md

…

surrounding_text.md

…