Add .hgignore.
Update instructions.

--HG--
extra : amend_source : 3e650def9ce1adc7438519f277b1967181aaab16
Added tag 2.4 for changeset 3d51dd49a731
Relocate icon.

--HG--
rename : static/src/img/icon.png => static/description/icon.png
Modifications to work with Odoo 8.0.