modify $grey-light bs color

Fixes #449 

This modifies the bootstrap default variable which is setting styles to #99999.   @jvine Does this meet our threshold in all situations? I am unable to find a situation which has a white background.

```
.text-muted, .appliedFilter .filterName:after, .facet-values li .remove, .search_history .filterName, .search_history .filterSeparator {
  color: #737373;
}
```