Move chai in the devDependencies
Move chai in the devDependencies

This commit also applies the version strategy suggestion (1b) explained in #50.
w3c/echidna,catataw/echidna,rrrene/echidna,w3c/echidna,w3c/echidna,rrrene/echidna,rrrene/echidna,catataw/echidna,catataw/echidna