Allow that branch names could be not valid as environment IDs, in 'checkout' command.
Allow that branch names could be not valid as environment IDs, in 'checkout' command.

See issue #207

pjcdawkins/platformsh-cli,platformsh/platformsh-cli,pjcdawkins/platformsh-cli,supriyantomaftuh/platformsh-cli,OriPekelman/platformsh-cli,mglaman/platformsh-cli,platformsh/platformsh-cli,mglaman/platformsh-cli,Fredplais/platformsh-cli,mglaman/platformsh-cli,platformsh/platformsh-cli,Fredplais/platformsh-cli,OriPekelman/platformsh-cli,supriyantomaftuh/platformsh-cli,Fredplais/platformsh-cli,pjcdawkins/platformsh-cli,supriyantomaftuh/platformsh-cli,OriPekelman/platformsh-cli