message: Add note for freshness issues
diff: * Added `NETWORK_MONITOR` role to NYM transaction builder.
  * Bugfixes
  +NOTE: This version of libindy will work slower with older versions of node due to freshness changes.
  +
  ## 1.7.0 - 2018-12-21
  * Added VCX - a library built over libindy for **V**erifiable **C**redentials e**X**change. API is EXPERIMENTAL.
  * At the current moment mobile builds are not available - they should be added in future releases.
  