Bootstrap3-styled file upload buttons

gistfile1.scss

.btn-file {
  position: relative;
  overflow: hidden;

  & input[type=file] {
    position: absolute;
    top: 0;
    min-width: 100%;
    max-width: 100%;
    min-height: 100%;
    font-size: 100%;
    text-align: right;
    filter: alpha(opacity=0);
    opacity: 0;
    outline: none;
    background: white;
    cursor: inherit;
    display: block;
  }
  &+.btn-file-filename {
    margin-left: 10px;
  }
}