Set github_api gem version

version 0.12.0 changed the API enough that it breaks jeweler.

`~> 0.11.0` should match the last working version, 0.11.3, until jeweler can be updated to use the new API.

Fixes technicalpickles#268

jeweler.gemspec

@@ -194,7 +194,7 @@ Gem::Specification.new do |s|
       s.add_runtime_dependency(%q<rake>, [">= 0"])
       s.add_runtime_dependency(%q<git>, [">= 1.2.5"])
       s.add_runtime_dependency(%q<nokogiri>, [">= 1.5.10"])
-      s.add_runtime_dependency(%q<github_api>, [">= 0"])
+      s.add_runtime_dependency(%q<github_api>, ["~> 0.11.0"])
       s.add_runtime_dependency(%q<highline>, [">= 1.6.15"])
       s.add_runtime_dependency(%q<bundler>, [">= 1.0"])
       s.add_runtime_dependency(%q<rdoc>, [">= 0"])
@@ -207,7 +207,7 @@ Gem::Specification.new do |s|
       s.add_dependency(%q<rake>, [">= 0"])
       s.add_dependency(%q<git>, [">= 1.2.5"])
       s.add_dependency(%q<nokogiri>, [">= 1.5.10"])
-      s.add_dependency(%q<github_api>, [">= 0"])
+      s.add_dependency(%q<github_api>, ["~> 0.11.0"])
       s.add_dependency(%q<highline>, [">= 1.6.15"])
       s.add_dependency(%q<bundler>, [">= 1.0"])
       s.add_dependency(%q<rdoc>, [">= 0"])
@@ -221,7 +221,7 @@ Gem::Specification.new do |s|
     s.add_dependency(%q<rake>, [">= 0"])
     s.add_dependency(%q<git>, [">= 1.2.5"])
     s.add_dependency(%q<nokogiri>, [">= 1.5.10"])
-    s.add_dependency(%q<github_api>, [">= 0"])
+    s.add_dependency(%q<github_api>, ["~> 0.11.0"])
     s.add_dependency(%q<highline>, [">= 1.6.15"])
     s.add_dependency(%q<bundler>, [">= 1.0"])
     s.add_dependency(%q<rdoc>, [">= 0"])