mail_to helper method fix

do not generate blank options in mailTo
when mail_to generate blank options for any passed options(cc, bcc, body, subject)
then MICROSOFT OUTLOOK treats it differently and set wrong values in different options.
So, I think we should not add blank options in link.

In windows outlook:

![outlook_issue-1](https://cloud.githubusercontent.com/assets/1930730/4492059/2a73a4d6-4a3e-11e4-891d-3a4693ac511a.png)

In other mail application
![screen shot 2014-09-23 at 6 24 56 pm](https://cloud.githubusercontent.com/assets/1930730/4492089/650e41b4-4a3e-11e4-8fc0-0456e88da5d6.png)