implemented v0.1 backend: see details for api docs

POST->
/budget -> create new budget
/transaction -> create new transaction
/expense -> create new expense
/fixed -> get fixed budget information
/flex -> get flex budget information
/analytics -> get budget analytics

PUT->
/expense -> update expense object

Added basic testing suite w/ 12 unit tests.

no FE work done yet...

Signed-off-by: Phil <prbaylog@gmail.com>