Added !important keyword to float: none; rule of centered columns in grid system

Added !important keyword to float: none; rule of centered columns in grid system
Currently selectors:
[class*="column"] + [class*="column"]:last-child { float: $opposite-direction; }
[class*="column"] + [class*="column"].end { float: $default-float; }
are more specific (specifity= 3) than rules for centered columns (specifity=2), and if centered
column is the last one in a row it will use f.e. float: right; rule instead of
float: none; from centered classes