update url to setup instructions (closes #520)

css/theme/README.md

 ## Dependencies
 
-Themes are written using Sass to keep things modular and reduce the need for repeated selectors across files. Make sure that you have the reveal.js development environment including the Grunt dependencies installed before proceding: https://github.com/hakimel/reveal.js#development-environment
+Themes are written using Sass to keep things modular and reduce the need for repeated selectors across files. Make sure that you have the reveal.js development environment including the Grunt dependencies installed before proceding: https://github.com/hakimel/reveal.js#full-setup
 
 
 
@@ -20,4 +20,4 @@ Declares a set of custom variables that the template file (step 4) expects. Can
 This is where you override the default theme. Either by specifying variables (see [settings.scss](https://github.com/hakimel/reveal.js/blob/master/css/theme/template/settings.scss) for reference) or by adding full selectors with hardcoded styles.
 
 4. **Include [/css/theme/template/theme.scss](https://github.com/hakimel/reveal.js/blob/master/css/theme/template/theme.scss)**
-The template theme file which will generate final CSS output based on the currently defined variables.
\ No newline at end of file
+The template theme file which will generate final CSS output based on the currently defined variables.