Flatly: Page-header border(-bottom) color

Hi!

As I decided to modify Flatly template I started using locally generated bootstrap.min.css file. But, then I noticed that bottom border is not showing on .page-header component. Here is the fix, hope it will help.

If you are using [bootstrap.min.css](http://netdna.bootstrapcdn.com/bootswatch/3.1.1/flatly/bootstrap.min.css) from MaxCDN, everything is working fine.

BTW, thx for the Bootswatch, great templates! :smiley_cat: