Expr func needs to be prefixed with "sq"

Otherwise we get an undefined error.
Add NotEq expression.
add a way to escape question mark while replacing question mark by a dollar sign
Merge pull request #32 from rande/escape_question_mark

add a way to escape question mark while replacing question mark by a dollar sign
Merge pull request #29 from ngdinhtoan/TN-01-not-equals

Add NotEq expression.
Merge pull request #28 from mjangda/bug/docs-Expr

Docs: Expr func needs to be prefixed with "sq"