Add css helper classes

[ZachTRice]

Add some basic css classes to help with development.

Block classes:
.clearfix
.left { float: left; }
.right { float: right; }

Text Classes:
.text-left { text-align: left; }
.text-right { text-align: right; }
.text-center { text-align: center; }
.text-justify { text-align: justify; }
.text-nowrap
.h1,.h2,.h3,.h4,.h5,.h6
.lead
...

More classes for consideration: http://getbootstrap.com/css/#overview

[ZachTRice]

We are introducing bootstrap 4 in PR #920 which includes all the classes listed above.