add space after function keyword in anonymous fns
add test for API DELETE verb

This commit adds a test for the DELETE verb for the API.  This deletes
an atm transaction from the array and then does a GET request to verify
the length of the array is reduced by one.  Also adds a space after the
function keyword but before the left paren to make the code style follow
Crockford's conventions.
add test suite for the 'purchase' model

This commit adds a test suite for the 'purchase' model, though only
tests the default instantiation--ie, with no args paramater passed.
Also adds default values to the purchase model in the event an empty arg
obj is passed in during instantiation.