v0.7.3

• Feature: Support Throwable when setting previous exception from server callback
  (#155 by @jsor)

• Fix: Fixed URI parsing for origin-form requests that contain scheme separator
  such as /path?param=http://example.com.
  (#209 by @aaronbonneau)

• Improve test suite by locking Travis distro so new defaults will not break the build
  (#211 by @clue)