Remove -i option (#704)

In-place editing should be implemented with builtins for file I/O.

tests/run

@@ -129,11 +129,6 @@ EOF
 printf '1\n'|./jq -ces --seq '. == [1]' >/dev/null 2> $d/out
 cmp $d/out $d/expected
 
-$VALGRIND $Q ./jq -n '0, 1, 2' > $d/a
-$VALGRIND $Q ./jq -n '3, 4, 5' > $d/b
-$VALGRIND $Q ./jq -i '.+1' $d/a $d/b
-$VALGRIND $Q ./jq -se '. == [1,2,3,4,5,6]' $d/a
-
 ## Test streaming parser
 
 ## If we add an option to stream to the `import ... as $symbol;` directive