Add a build task to validate LINQPad samples (#1551)

* add a build task to run LINQPad samples

* make modifications to the validation of LINQPad samples

* rename the CAKE task to its original name ValidateLINQPadSamples
* rename the LINQPad samples file so they get executed in ordinal order (1, 2, ..., 10 and not 1, 10, 2, ...)

* remove openssl linking in TravisCI when on macOS

samples/linqpad-samples/05-interact-with-git-database.linq

@@ -0,0 +1,35 @@
+<Query Kind="Program">
+  <NuGetReference>Octokit</NuGetReference>
+  <NuGetReference>Octokit.Reactive</NuGetReference>
+  <NuGetReference>Rx-Main</NuGetReference>
+  <Namespace>Octokit</Namespace>
+  <Namespace>System.Threading.Tasks</Namespace>
+</Query>
+
+async Task Main(string[] args)
+{
+	var owner = string.Empty;
+	var reponame = string.Empty;
+	
+	GitHubClient client = new GitHubClient(new Octokit.ProductHeaderValue("Octokit.samples"));
+	
+	owner = "octokit";
+	reponame = "octokit.net";
+
+
+	var releases = await client.Repository.Release.GetAll(owner, reponame);
+
+	// we have to build up this tag because release tags
+	// are just lightweight tags. you can read more about
+	// the differences between lightweight tags and annotated tags
+	// here: http://git-scm.com/book/en/Git-Basics-Tagging#Creating-Tags
+	
+	// we can fetch the tag for this release
+	var reference = "tags/" + releases[0].TagName;
+	var tag = await client.Git.Reference.Get(owner, reponame, reference);
+	tag.Dump();
+	
+	// and we can fetch the commit associated with this release
+	var commit = await client.Git.Commit.Get(owner, reponame, tag.Object.Sha);
+	commit.Dump();
+}