Docs: Updated roadmap issue to link to the pinned roadmap issues

ROADMAP.md

-# Roadmap (2018-08-07)
-
 This roadmap is a tentative plan for the core development team. Things change constantly as PRs come in and priorities change. 
 This roadmap is a tentative plan for the core development team. Things change constantly as PRs come in and priorities change. 
 But it will give you an idea of our current vision and plan. 
 But it will give you an idea of our current vision and plan. 
   
   
-### Short term (1-2 months)
-  - PRs & Bugs
-  - React Panel Support
-  - React Query Editor Support
-  - Metrics & Log Explore UI 
-  - Grafana UI library shared between grafana & plugins
-  - Seperate visualization from panels
-  - More reuse between Explore & dashboard
-  - Explore logging support for more data sources 
-   
-### Mid term (2-4 months)  
-  - Drilldown links
-  - Dashboards as code workflows 
-  - React migration
-  - New panels 
-  
-### Long term (4 - 8 months)
- - Alerting improvements (silence, per series tracking, etc)
-
-### In a distant future far far away
- - Meta queries 
- - Integrated light weight TSDB
- - Web socket & live data sources
-
-### Outside contributions
-We know this is being worked on right now by contributors (and we hope to merge it when it's ready). 
-
+Go to the Issues tab on GitHub. There you will find, at the top, 3 pinned roadmap issues.