v1.2.0

Quite a few changes to reflect new behavior around identity keys rolled
out in the Signal apps in June 2017:
  - We always trust a new identity key when receiving messages
  - We have a few requirements for trust when sending messages:
    1) it can't have changed very recently
    2) if the previous identity key had been verified by the user, the
       user needs to explicitly approve a new identity key

Expose ability to delete all existing sessions - for proper reset (#35)

Allow caller to provide fillMessageKeys limit - allowing customization
  of the maxiumum number of one-sided messages in a conversation (#29)

Dev:
  - A number of changes to make the branch build in CI, add badge, etc.

Note: we appear to have some unreliability during our Firefox 34 builds
on Sauce. A little less than half the time the test fails with an out of
memory error.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "libsignal-protocol",
   "repository": "https://github.com/WhisperSystems/libsignal-protocol-javascript.git",
-  "version": "1.1.2",
+  "version": "1.2.0",
   "license": "GPL-3.0",
   "dependencies": {
     "long": "^3.1.0",