Version 0.1.5: Bug fixes and new functions

Functions added:

• sha256 (contributed by @paurue)
• sum
• any (contributed by @ecerulm)
• all (contributed by @ecerulm)

Bugs fixed:

• number(<input>, <fallback>) now handles the input not being a string or a number,
• issue #41: NullpointerException in object matcher, and
• issue #9: Make operators left-associative instead of right-associative