Fixed broken links. See #326

@Regina.Hightower reported some issues with broken links on the front
page. Changed the links from `../path/to/page.html` to
`path/to/page.html`. This worked on local testing with `mkdocs serve`
command. It should also work at `docs.opengrid.io/en/dev/`.

docs/index.md

@@ -12,7 +12,7 @@ n-->
 OpenGrid can be used for real-time data analysis, refreshing frequently to provide the most up-to-date information. It also allows users to reach back into time to look at past events.
 
 ### Technical Architecture
-OpenGrid is designed to be flexible with different types of data sources. Whether it's MongoDB, a RESTful API, or other data sources, programmers can use [OpenGrid's API](../system-administration/opengrid-api#rest-service-resources) and [Service Layer](../system-administration/installation-and-setup#service-layer) to program it to work with other data sources.
+OpenGrid is designed to be flexible with different types of data sources. Whether it's MongoDB, a RESTful API, or other data sources, programmers can use [OpenGrid's API](system-administration/opengrid-api#rest-service-resources) and [Service Layer](system-administration/installation-and-setup#service-layer) to program it to work with other data sources.
 
 ### Open Source
 Open source gives "OpenGrid" its name. Feel free to use it, contribute to it, or change it. Just please take a look at the project's <a href="https://github.com/Chicago/opengrid/blob/master/LICENSE.md">license</a>.