headers will be formatted automatically now
added default formatter

reports may now implement a override a method called format_column
that will be passed the column and value being formatted. By default
this will return the value.  This method will only be called if a
column specific formatter method is not found
fixes #3
Merge branch 'master' of github.com:adamhunter/dossier

Conflicts:
	CHANGELOG.md
	lib/dossier/result.rb