add transparent support for custom logo #148

p.s.: maybe also need to update the phrase: "Please upload a file in %s formats with a minimum height of %s pixels."? For me loaded a smaller height size than is written in the settings (just increased).

Please can you explain what the error due to? I did not work with Travis CI, I can not understand what the cause of the error. Error applies only to commit 53febf0?

Thank you.

Thank you for this nice little new feature! I committed it as part of: http://dev.piwik.org/trac/ticket/4368#ticket

PS: the build failure was a random failure also affecting git master, which we fixed since