adds user router for handling transactions and clarifies comments in middleware chain to reflect routing structure
adds getAccount function for returning account details of give user
sets up minimal router for user transactions
fixes typo in query
adds some basic parameter checking and sets up get-user route
adds function to validate currency and quantity parameters
changes buy function to take callback
implements buy route
changes helper function to take a callback
adds sell route
Merge branch 'master' of https://github.com/RP-3/Cryptocent-API