Add UT around probes

[Kawacrepe]

The goal is to add UT about https://github.com/NodeSecure/js-x-ray/tree/master/src/probes/

It can help you to get into this project, feel free to submit a PR about 1 or multiples probes :)

[tony-go]

Neat!

[fraxken]

List of probes that still need contribution.

Note
Please contribute and create merge request for one probe at a time.

Already done:

• isLiteralRegex (contributed by @fraxken)
• isUnsafeCallee (contributed by @Kawacrepe)
• isWeakCrypto (contributed by @tony-go)
• isFunctionDeclaration
• isObjectExpression
• isBinaryExpression
• isRegexObject
• isMemberExpression
• isAssignmentExpression
• isImportDeclaration
• isRequire
• isArrayExpression
• isUnaryExpression
• isVariableDeclaration
• isLiteral

If you are new to the project or we didn't had any opportunity to deal with an AST (Abstract Syntax Tree) i highly recommend you to contribute to the first group of probes.