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/regression_test.go

@@ -0,0 +1,22 @@
+package matrix
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestPoly(t *testing.T) {
+	assert := assert.New(t)
+	var xGiven = []float64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+	var yGiven = []float64{1, 6, 17, 34, 57, 86, 121, 162, 209, 262, 321}
+	var degree = 2
+
+	c, err := Poly(xGiven, yGiven, degree)
+	assert.Nil(err)
+	assert.Len(c, 3)
+
+	assert.InDelta(c[0], 0.999999999, DefaultEpsilon)
+	assert.InDelta(c[1], 2, DefaultEpsilon)
+	assert.InDelta(c[2], 3, DefaultEpsilon)
+}