git-cola.rst: mention using LANGUAGE environment variable to switch language

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
git-cola.rst: fix reStructuredText syntax

This commit adds the missing "Literal Blocks" syntax to commit 805ff555

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>
Merge pull request #293 from Vdragon/improve_documentation

git-cola.rst: mention using LANGUAGE environment variable to switch language

Signed-off-by: David Aguilar <davvid@gmail.com>