Improvements to contact display

Tags added to contact index. Tag field added to contact#show. Addresses
no longer show blank lines or orphaned commas when fields are missing
data.
Extended array to clean blank elements

A common problem is removing nil and empty elements in an array. This
extends array with .clean which rejects all blank? elements (empty or
nil).
Tag separator set to colon ":"

For now we will use a colon as a tag separator. In the tag field on
contact#show the colon makes a nice looking line of tags.