Fixing errors in Github-flavored markdown

Whitespace between the closing brackets and opening parenthesis of markdown links prevented github from rendering the links.

CONTRIBUTING.md

@@ -2,8 +2,8 @@ Want to contribute? Great! First, read this page (including the small print at t
 
 ### Before you contribute
 Before we can use your code, you must sign the
-[Google Individual Contributor License Agreement]
-(https://cla.developers.google.com/about/google-individual)
+[Google Individual Contributor License Agreement](
+https://cla.developers.google.com/about/google-individual)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
 copyright to your changes, even after your contribution becomes part of our
 codebase, so we need your permission to use and distribute your code. We also
@@ -23,5 +23,5 @@ use Github pull requests for this purpose.
 ### The small print
 Contributions made by corporations are covered by a different agreement than
 the one above, the
-[Software Grant and Corporate Contributor License Agreement]
-(https://cla.developers.google.com/about/google-corporate).
+[Software Grant and Corporate Contributor License Agreement](
+https://cla.developers.google.com/about/google-corporate).