[FIX] email_template: Fixed 'mail.compose.message' to show the email con...

...tent of resource record in template's langunage.(maintenance: 617309)

Hi,

If any "Email Template" is set to use some language for it and when any resource model's record is rendered using that template then that record should fully be rendered in that language. But currently, the field values of resource record is not being rendered in that language, instead, it is using the current user's language.

You can see in below image, the values for fields "Pricelist(FR)" and "Payment Term(FR)" aren't rendered in template's language, which I set it as "fr_BE",
![email_template_rendering_issue](https://cloud.githubusercontent.com/assets/7601649/5083054/1a426b7e-6f14-11e4-8d33-12b561a736b0.png)


This branch fixes this issue, kindly review it.

Thanks.