Improve tag definition

The current code requires that tags must be defined as:
```julia
[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:

```julia
# as an array of pairs
["foo" => "bar", "missy" => "gala"]

# as a key-value singular dict
Dict("foo" => "bar", "missy" => "gala")
```