Improve tag definition

[pebeto]

The current code requires that tags must be defined as:

[Dict("key" => "foo", "value" => "bar"), Dict("key" => "missy", "value" => "gala")]

but what about making all the logic behind to allow the user define the tags as:

# as an array of pairs
["foo" => "bar", "missy" => "gala"]

# as a key-value singular dict
Dict("foo" => "bar", "missy" => "gala")

[pebeto]

A solution was implemented in #59 .