Use simplejson library instead of json

[daniel-vera-rodriguez]

We need to serialize a Decimal object in the json object.

For this reason, only changing simplejson library instead of json, we can do it.

[jespino]

Hi Daniel,

I'm open to change to simplejson but allowing to use builtin json library, something like

try:
    import simplejson as json
except ImportError:
    import json

And removing the requirement in the installation.

Anyway, you can overwrite the JSONEncoder to allow to encode Decimals without the need of simplejson (you can see an example here: http://stackoverflow.com/questions/1960516/python-json-serialize-a-decimal-object)

[niwinz]

Adding support for decimal types can be done with native json module without adding new dependency I think...

[coveralls]

Coverage increased (+0.1%) to 64.69% when pulling f6699cc on daniel-vera-rguez:master into f6ab7ce on jespino:master.

[jespino]

Thanks! ✨

[daniel-vera-rodriguez]

Hi guys!

I did the change that @jespino proposed. I had been already seen the link of Stack Overflow and, in fact, in second answer I saw the use of simplejson. I thought that that solution could be less invasive.

But, thank you very much both!