Update contact model

RELEASE.md

@@ -1,3 +1,27 @@
+# Release Note (version 0.2.1)
+
+## Developer Note
+
+Contact model between two different rods and rod with itself is implemented. 
+Testing the contact model is done through simulations. These simulation scripts can be found under
+[RodContactCase](./RodContactCase). 
+However, in future releases we have to add unit tests for contact model functions to test them and increase code coverage.
+
+## Notable Changes
+- #31: Merge contact model to master [PR #40 in public](https://github.com/GazzolaLab/PyElastica/pull/40)
+
+### Release Note
+<details>
+  <summary>Click to expand</summary>
+
+- Rod-Rod contact and Rod self contact is added.
+- Two example cases for rod-rod contact is added, i.e. two rods colliding to each other in space. 
+- Two example cases for rod self contact is added, i.e. plectonemes and solenoids.
+
+</details>
+
+---
+
 # Release Note (version 0.2)
 
 ## Developer Note

elastica/_elastica_numba/_joint.py

@@ -1,5 +1,12 @@
 import warnings
-from elastica.joint import ExternalContact
+
+from elastica.joint import (
+    FreeJoint,
+    HingeJoint,
+    FixedJoint,
+    ExternalContact,
+    SelfContact,
+)
 
 warnings.warn(
     "The numba-implementation is included in the default elastica module. Please import without _elastica_numba.",