Fixing Wrong Generated First Set

[MammarDr]

Issue #138
Hi this is my first github contribution and i feel honored to be help to you as you were to me in your amazing courses.

1-
I fixed the wrong generated first sets from productions that have the nullable LHS(derive ε) appear in firstOf(rhs).

Grammar:
B -> B "a" | ε

Without fix:
First(B) = { ε }

With fix:
First(B) = { "a", ε }

the solution is to register the Non-Terminals that derive epsilon directly (A->ε) before calculating the first sets.

added test case for this issue.

2-
i also spotted a function typo 'getOrignialSymbol' -> 'getOriginalSymbol'

[DmitrySoshnikov]

MammarDr, thanks for the contribution - glad we have this bug finally caught! Please see comments on the formatting (use tools which should be in this repo for auto-format the code to single style).