chore: update travis build command (#970)

Author: thinkingserious

.travis.yml

@@ -1,5 +1,6 @@
 language: csharp
 dotnet: 1.0.4
+solution: SendGrid.sln
 os: linux
 dist: trusty
 mono: latest
@@ -26,7 +27,7 @@ after_success:
 deploy:
   skip_cleanup: true
   provider: script
-  script: dotnet nuget push ./src/SendGrid/bin/Release/SendGrid.*.nupkg --api-key $NUGET_API_KEY --source https://api.nuget.org/v3/index.json
+  script: nuget push ./src/SendGrid/bin/Release/SendGrid.*.nupkg --api-key $NUGET_API_KEY --source https://api.nuget.org/v3/index.json
   on:
     branch: master
     tags: true