Update Travis CI config to handle coverage on Perl 5.8

.travis.yml

@@ -2,7 +2,6 @@ sudo: false
 
 language: perl
 perl:
-    - "5.8"
     - "5.10"
     - "5.12"
     - "5.14"
@@ -13,13 +12,22 @@ perl:
     - "5.24"
     - "5.26"
 
+env:
+    - OLD_DEVEL_COVER=0
+
+matrix:
+    include:
+        - perl: 5.8
+          env: OLD_DEVEL_COVER=1
+
 before_install:
     - git clone git://github.com/travis-perl/helpers ~/travis-perl-helpers
     - source ~/travis-perl-helpers/init --auto
 
 install:
     - cpanm --quiet --installdeps --notest .
-    - cpanm --quiet --notest Devel::Cover@1.23
+    - if [ "$OLD_DEVEL_COVER" = "0" ]; then cpanm --quiet --notest Devel::Cover; fi
+    - if [ "$OLD_DEVEL_COVER" = "1" ]; then cpanm --quiet --notest Devel::Cover@1.23; fi
     - cpanm --quiet --notest Devel::Cover::Report::Coveralls
 
 script: