Merge pull request #5 from hsharrison/master

Fix ignored pair input to MarketDatabase.retrieve* functions

Thanks!
Added reminder to refactor.
Merge branch 'master' of https://github.com/alanmcintyre/btce-bot
Removed default value for pair in retrieveDepth, as the method body assumes it is not None.
Added refactoring reminder.
Added check that sell price is above buy price.
Added shebang to sample scripts.