Adds initial test framework; adds PrivateKey.from_nsec() (#13)

* Adds initial test framework; adds PrivateKey.from_nsec()

* Update setup.py

test/test_key.py

@@ -0,0 +1,23 @@
+from nostr.key import PrivateKey
+
+
+def test_eq_true():
+    """ __eq__ should return True when PrivateKeys are equal """
+    pk1 = PrivateKey()
+    pk2 = PrivateKey(pk1.raw_secret)
+    assert pk1 == pk2
+
+
+def test_eq_false():
+    """ __eq__ should return False when PrivateKeys are not equal """
+    pk1 = PrivateKey()
+    pk2 = PrivateKey()
+    assert pk1.raw_secret != pk2.raw_secret
+    assert pk1 != pk2
+
+
+def test_from_nsec():
+    """ PrivateKey.from_nsec should yield the source's raw_secret """
+    pk1 = PrivateKey()
+    pk2 = PrivateKey.from_nsec(pk1.bech32())
+    assert pk1.raw_secret == pk2.raw_secret