Fixing requirements.
Adding development requirements.
Adding support to differents delivery services.

Differents delivery services were already supported, but SEDEX, serivce
was hard-coded.
Fixing exception handling.
Fixing functional test.

Using PAC as the default freight type.
Adding E-SEDEX code field.

The e-SEDEX service code is different by each carrier user.
Adding esedex_code migration.