Added new overloads to LeftAssociative, RightAssociative and Unary

[gumbarros]

This closes #127

[gumbarros]

Unary W.I.P, I'm still stuck:

        /// <summary>
        /// Builds a parser that creates a unary operation.
        /// </summary>
        /// <typeparam name="T">The type of the returned parser.</typeparam>
        /// <typeparam name="TInput">The type of the symbol parsers.</typeparam>
        /// <param name="parser">The higher-priority parser the symbols are separating.</param>
        /// <param name="ops">The array of operators that can be parsed.</param>
        /// <param name="factory">The factory method to create the result of the operation.</param>
        /// <returns>A parser that creates a unary operation.</returns>
        public static Parser<T> Unary<T, TInput>(this Parser<T> parser, Parser<TInput>[] ops, Func<TInput, T, T> factory)
        {
            var choices = ops.Select(op => new Then<TInput, Func<T, T>>(op, operation => a => factory(operation, a)));

            return Recursive<T>(u =>
            {
                var unaryChoices = choices.Select(choice => choice.Then(u));
                return new OneOf<T>(unaryChoices.ToArray()).Or(parser);
            });
        }

        [Theory]
        [InlineData("2", 2)]
        [InlineData("-2", -2)]
        [InlineData("--2", 2)]
        public void ShouldParsePrefixWithAlternativeOverload(string expression, double result)
        {
            var primary = Terms.Double();

            var negate = Terms.Char('-').Then(_ => (Func<double, double>)(a => 0 - a));

            var unary = primary.Unary([negate], (operation, a) => operation(a));

            Assert.Equal(result, unary.Parse(expression));
        }

Argument type 'Parlot.Fluent.Parser<Parlot.Fluent.Deferred>[]' is not assignable to parameter type 'Parlot.Fluent.Parser[]'

@sebastienros do you know how can I use T instead of Deferred<T> in this case?