Default text-direction icon is RTL instead of LTR

[benbro]

[Describe the issue]
The text-direction icon is indicating right-to-left by default instead of left-to-right.
The icon when inactive should be flipped.

In addition, when active in RTL mode, I don't think the icon should be light blue, it should just stay black.

Steps for Reproduction

1. Visit http://beta.quilljs.com/docs/formats/
2. Type few characters

Expected behavior: [expected]
The arrow in the text-direction button should point from left to right (LTR) by default.

Actual behavior: [actual]
The arrow point from right (RTL)

Platforms: [ex. Chrome 48 on Mac 10.11]
Firefox 46 on Windows 7

Version: [version]
1.0-Beta.1