Add helpful error message when there is a problem with deploy.rb or a custom Rakefile
Add helpful error message when there is a problem with deploy.rb or a
custom Rakefile

fixes #36

ianks/mina,whhx/mina,cyberwolfru/mina,openaustralia/mina,estum/mina,flowerett/mina,openaustralia/mina,scalp42/mina,mfinelli/mina,allantatter/mina,dcalixto/mina,cyberwolfru/mina,estum/mina,flowerett/mina,whhx/mina,Zhomart/mina,ianks/mina,scalp42/mina,allantatter/mina,stereodenis/mina,Zhomart/mina,dcalixto/mina,mfinelli/mina