doc: updated the minimum versions of ngx_lua or ngx_openresty require…

…d by this library.

doc: markdown formatting fixes.

bumped version to 0.13.

bumped version to 0.12.

bumped version to 0.11.

bumped version to 0.10.

bumped version to 0.09.

Merge branch 'master' of github.com:agentzh/lua-resty-mysql

bumped the version number.

feature: added _VERSION field. also bumped version number to 0.06.