Merged css->html (avoid link dep.)

Moved the css within the head of the html to avoid issues
with linking dependencies (i.e. that outfile, depending on where
it is output to, will not be able to find the css unless this
is swithed to abs path)

Also, added some default values to invoice.html to clean up
template.
added decimal val to test.json
Ubuntu currency precision fix

Replaced problematic locale string with basic 2 precision formatting.
This may be disadvantageous for supporting multiple country currency.

Also, removed print statement in invoice, main(), replaced with return.
Merge pull request #3 from mekarpeles/bug/price-precision-err

Bug/price precision err, you renamed it to envois, not envoi. That's fine (it's the plural version).