Fix #107: support ghc-8.8 (#108)

* Fix #107: support ghc-8.8

* Add travis build for ghc 8.8.1

.travis.yml

@@ -22,6 +22,7 @@ env:
  - CABALVER=2.0  GHCVER=8.2.2
  - CABALVER=2.2  GHCVER=8.4.1
  - CABALVER=2.4  GHCVER=8.6.1
+ - CABALVER=2.4  GHCVER=8.8.1
 
 # Note: the distinction between `before_install` and `install` is not
 #       important.

protolude.cabal

@@ -26,7 +26,8 @@ tested-with:
   GHC == 8.0.1,
   GHC == 8.2.1,
   GHC == 8.4.1,
-  GHC == 8.6.1
+  GHC == 8.6.1,
+  GHC == 8.8.1
 extra-source-files: README.md CHANGES.md
 
 Source-Repository head
@@ -66,13 +67,13 @@ library
     -fwarn-implicit-prelude
 
   build-depends:       
-    base                >= 4.6  && <4.13,
+    base                >= 4.6  && <4.14,
     array               >= 0.4  && <0.6,
     ghc-prim            >= 0.3  && <0.6,
     async               >= 2.0  && <2.3,
     deepseq             >= 1.3  && <1.5,
     containers          >= 0.5  && <0.7,
-    hashable            >= 1.2  && <1.3,
+    hashable            >= 1.2  && <1.4,
     transformers        >= 0.2  && <0.6,
     text                >= 1.2  && <1.3,
     stm                 >= 2.4  && <2.6,