chore: fix case of GitHub (#1497)

Author: jbampton

_posts/2012-05-25-elixir-v0-5-0-released.markdown

@@ -27,7 +27,7 @@ Around February of that year, feeling confident enough about the direction the l
 
 One of the goals we have set was to have a good website and documentation before the next official release. With the help of the Plataformatec team, we created a logo for Elixir and put this website live.
 
-At the same time, [we were working on pygments support](https://bitbucket.org/birkenfeld/pygments-main/pull-request/57/add-elixir-and-elixir-console-lexers), a [documentation generation tool](https://github.com/elixir-lang/ex_doc) and many others. Soon, Github was able to syntax highlight Elixir code and [our API documentation was online](/).
+At the same time, [we were working on pygments support](https://bitbucket.org/birkenfeld/pygments-main/pull-request/57/add-elixir-and-elixir-console-lexers), a [documentation generation tool](https://github.com/elixir-lang/ex_doc) and many others. Soon, GitHub was able to syntax highlight Elixir code and [our API documentation was online](/).
 
 At the same time, people started to gather around #elixir-lang channel on irc.freenode.net and [play with Elixir](https://github.com/elixir-lang/elixir/tree/master/lib/mix), [start their](https://github.com/guedes/exdate) [own projects](https://github.com/yrashk/validatex) and [tutorials](https://github.com/alco/elixir/wiki/Erlang-Syntax:-A-Crash-Course).
 

install.markdown

@@ -149,7 +149,7 @@ $ cd elixir
 $ make clean test
 ```
 
-If the tests pass, you are ready to go. Otherwise, feel free to open an issue [in the issues tracker on Github](https://github.com/elixir-lang/elixir).
+If the tests pass, you are ready to go. Otherwise, feel free to open an issue [in the issues tracker on GitHub](https://github.com/elixir-lang/elixir).
 
 ## Installing Erlang