Bump upper bound of either.

Author: tmcgilchrist

Diff for: airship.cabal

@@ -2,7 +2,7 @@ name:                 airship
 synopsis:             A Webmachine-inspired HTTP library
 homepage:             https://github.com/helium/airship/
 Bug-reports:          https://github.com/helium/airship/issues
-version:              0.9.1
+version:              0.9.2
 license:              MIT
 license-file:         LICENSE
 author:               Reid Draper and Patrick Thomson
@@ -51,7 +51,7 @@ library
                       , containers
                       , cryptohash              == 0.11.*
                       , directory
-                      , either                  >= 4.3     && < 4.6
+                      , either                  >= 4.3     && < 6.0
                       , filepath                >= 1.3     && < 1.5
                       , http-date
                       , http-media