Fix Contribution Guide link

[ArtsiomMusin]

There is an issue with the Contribution Guide link from the Welcome page. It gets 404 as it points to an html file and not an md file.

My proposal is to remove the link at all and rename 'Contribution Guide.md' to ContributionGuide.md. The reason is that there is the Foundation documentation mentioned(see the first line in the paragraph I changed). So in github you won't see links, but if you run 'rake rdoc' and take a look at new docs, you can see that: I thought the same approach would be good. No links in github, but links in the html docs.

Another fix could be just to fix the ContributionGuide_md.html link to ContributionGuide.md. On another hand, it will be a bug for the generated docs as md links are not converted to html links. This is why I opened #121 to fix CLA and CCLA links. So to see those 404 errors, you need to generate docs by 'rake rdoc' and go to softlayer-ruby/doc/ContributionGuide_md.html.

Open for discussion what could be better to fix...

[coveralls]

Coverage remained the same at 99.762% when pulling aa136e6b6e3bc10da8e232f91a8780efebf6d3b6 on ArtsiomMusin:fix-contribution-guide-links into 0adc74b10d89f9ed840b08c70186ee02ea531c2b on softlayer:master.

[renier]

I think keeping the links working on github (since that is how most people will browse) is important.

Maybe something can be done in the template rdoc uses to fix the links to md files.

<script>
for (var i = 0; i < links.length; i++) {
    if (links[i].href.endsWith(".md")) {
        links[i].href.slice(0, links[i].href.length-3) + ".html";
    }
}
</script>

[coveralls]

Coverage remained the same at 99.762% when pulling e63f1d7328c2a3e1ec925f458fbee15097c47a19 on ArtsiomMusin:fix-contribution-guide-links into d8049241d8e77ddb6cea0cc39793367037cd364f on softlayer:master.