Remove useless style.

Author: Tina C Lin (RD-TW)

src/btn-style.styl

@@ -148,7 +148,6 @@
     color: #222;
     background-color: #fff;
     background-image: linear-gradient(to bottom, #fff 0%, #fff 100%);
-    background-image: none! important;
     background-repeat: repeat-x;
     border-color: #ccc;
     transition: all .2s linear 0s