Adds matrix sub package & adds polynomial regression series (#36)

* updates

* updates

* tests.

* test coverage

* fixing test

* stride not rows + cols

* lu decomp implementation.

* poly regression!

* poly regression works.

* typo.

matrix/vector.go

@@ -0,0 +1,17 @@
+package matrix
+
+// Vector is just an array of values.
+type Vector []float64
+
+// DotProduct returns the dot product of two vectors.
+func (v Vector) DotProduct(v2 Vector) (result float64, err error) {
+	if len(v) != len(v2) {
+		err = ErrDimensionMismatch
+		return
+	}
+
+	for i := 0; i < len(v); i++ {
+		result = result + (v[i] * v2[i])
+	}
+	return
+}