fix centering on IE

Turns out the wordsearch centering for IE worked in the blockly app, but not in dashboard.  I don't fully understand why, but it has something to do with line-height screwing up the bounding box.  I did this by creating a rect for the bounding box so that I could see what it looks like.

Here it is with no line-height specified (bounding box for second row):
![image](https://cloud.githubusercontent.com/assets/1767466/3331243/78db2ccc-f7da-11e3-9d40-7777d1be5ea7.png)

Here it is with line-height at 120%:
![image](https://cloud.githubusercontent.com/assets/1767466/3331252/94c3cbc4-f7da-11e3-86cf-89d5018507ae.png)

I'd also tried setting it at 100%, where things did not work correctly.

(In both cases the bounding boxes are from before the transform, so the pictures may not make it quite clear how off they were).

Validated on BS IE 11, Mac FF Chrome and Safari.