Update CHANGELOG for 0.7

Author: hdevalence

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 Entries are listed in reverse chronological order.
 
+## 0.7.0
+
+* Update `curve25519-dalek`, `merlin` dependencies to 2.0.
+* Switch from `failure` to `thiserror` to provide `std`-compatible errors.
+* Correct `curve25519-dalek` feature-selection logic.
+
 ## 0.6.2
 
 * Correct minimum `curve25519-dalek` version to 1.0.3, not 1.0.0.