Varify that the needed env vars are set
Implemented search command
"yo get" doesn't need market explicitly anymore
Added -n argument to command for "noop" to display curl command

The "-n" option mean no-op, meaning do not execute the operation but instead
show the curl command that was supposed to be executed.
Moved yo_usage to the top of the file for clarity
Renamed internal function yo_curl to yo_internal_curl
URL encode the search query parameter

This allows to search for things with special characters like spaces:

yo search 'desperate house'