Update functions.pm
Update functions.pm

Minor fix to a typo from compouds -> compounds
cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools,cshenry/fba_tools