use nicer button/link for file selection, autoselect

[mfrederickson]

Using this information below, perhaps you could get rid of the default file upload button, and optionally trigger the file selection to come up initially. From https://developer.mozilla.org/en-US/docs/Using_files_from_web_applications#Using_hidden_file_input_elements_using_the_click()_method

Using hidden file input elements using the click() method

Starting in Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1), you can hide the admittedly ugly file element and present your own interface for opening the file picker and displaying which file or files the user has selected. You can do this by styling the input element with display:none and calling the click() method on the element.

[awojtczyk]

Please see: #11