Shift addon to linux only

Who knows if this works? The docs are terrible and the Travis linter
utterly borked.

.travis.yml

@@ -1,6 +1,12 @@
 language: csharp
 solution: ImageSharp.sln
 
+env:
+  global:
+   # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
+   #   via the "travis encrypt" command using the project repo's public key
+   - secure: "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"
+
 matrix:
   include:
     - os: linux # Ubuntu 14.04
@@ -8,6 +14,17 @@ matrix:
       sudo: required
       dotnet: 1.0.0-preview2-003121
       mono: latest
+      before_install:
+      - echo -n | openssl s_client -connect scan.coverity.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sudo tee -a /etc/ssl/certs/ca-
+      addons:
+          coverity_scan:
+          project:
+              name: "JimBobSquarePants/ImageSharp"
+              description: "Build submitted via Travis CI"
+          notification_email: james_south@hotmail.com
+          build_command_prepend: "dotnet restore"
+          build_command:   "dotnet build -c Release"
+          branch_pattern: master
     - os: osx # OSX 10.11
       osx_image: xcode7.2
       dotnet: 1.0.0-preview2-003121
@@ -20,23 +37,4 @@ branches:
 script:
   - cd src/ImageSharp/
   - dotnet restore
-  - dotnet build -c Release
-
-env:
-  global:
-   # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
-   #   via the "travis encrypt" command using the project repo's public key
-   - secure: "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"
-
-before_install:
-      - echo -n | openssl s_client -connect scan.coverity.com:443 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | sudo tee -a /etc/ssl/certs/ca-
-
-addons:
-  coverity_scan:
-    project:
-      name: "JimBobSquarePants/ImageSharp"
-      description: "Build submitted via Travis CI"
-    notification_email: james_south@hotmail.com
-    build_command_prepend: "dotnet restore"
-    build_command:   "dotnet build -c Release"
-    branch_pattern: master
+  - dotnet build -c Release