Make theme cards align left instead of center

Instead of center justifying the theme cards, this makes it so they align
left

closes: CNVS-29109

Test Plan:
- Go to Theme Collection view
- All theme cards should now align to the left, instead of centered

Example:
https://www.dropbox.com/s/smz9a4ruojl461r/Screenshot%202016-05-11%2014.18.10.png?dl=0

Change-Id: Id24b5896d286c909e93e7ae5b67b63e353f40a8e
Reviewed-on: https://gerrit.instructure.com/79347
Reviewed-by: Pam Hiett <phiett@instructure.com>
Reviewed-by: Chris Hart <chart@instructure.com>
Tested-by: Jenkins
QA-Review: Nathan Rogowski <nathan@instructure.com>
Product-Review: Colleen Palmer <colleen@instructure.com>

app/stylesheets/bundles/brand_config_index.scss

@@ -8,7 +8,6 @@
 .ic-ThemeCard-container__Main {
   display: flex;
   flex-wrap: wrap;
-  justify-content: space-around;
 }
 
 .ic-ThemeCard-container__Heading {