Pure Grid Units break in IE7

[tilomitra]

The grid breaks when you have grid units that span multiple rows. Here's a fiddle that demonstrates the breakage:

http://jsfiddle.net/C4PQQ/2/

On IE7, you see this:

I believe this has to do with how IE rounds sub-pixel values. I have a fix for this in #147. In the fiddle, uncomment the new .pure-u-* classes to see the fix.

The new *widths were determined by incrementally decreasing from the width until I got it to reliably work with a various permutations of different grid unit widths.

@thierryk ran into a similar issue on his work with YUI Grids. A similar solution is also used by Bootstrap for their fluid grids. However, I found the Bootstrap *width subtracts too much from the width. We ideally want those two values to be as close as possible.

[ericf]

I cannot reproduce:

[kunl]

同样的问题，pure-u-_-_不能占满全行

[fuwaneko]

IE7? Really? I mean it's 7 years old browser and it is not supported by Microsoft anymore.