Added support for guards in Argon

[SarthakKumar1997]

As per issue #35, adds functionality to detect guarded statements in Haskell. For example, the below function now displays the correct cyclomatic complexity of 4, instead of 2:

nthElement :: [a] -> Int -> Maybe a 
nthElement [] a = Nothing
nthElement (x:xs) a | a <= 0 = Nothing
                    | a == 1 = Just x
                    | a > 1 = nthElement xs (a-1)

[rubik]

Thanks, nice work!

[SarthakKumar1997]

No worries :)