Added a reference to the skeleton_app in README.md

Provided a short description of the skeleton app with a link to its repository.
This reference was placed under the Other cFS related elements/tools/apps/distributions section, under the Other Apps category.

Resolves: #68

README.md

@@ -136,6 +136,7 @@ The following list is user submitted, and not CCB controlled.  They are released
     - SCA: Stored Command Absolute application at https://github.com/nasa/SCA
     - SCH: Scheduler application at https://github.com/nasa/SCH
     - TO: Telemetry Output application at https://github.com/nasa/CFS_TO
+    - Skeleton App: A bare-bones application to which you can add your business logic at https://github.com/nasa/skeleton_app 
   - Other Interfaces
     - SIL: Simulink Interface Layer at https://github.com/nasa/SIL
     - ECI: External Code Interface at https://github.com/nasa/ECI