Change markdown extension to .md

diff --git a/basics.mdwn b/basics.md
similarity index 100%
rename from basics.mdwn
rename to basics.md

diff --git a/building.mdwn b/building.md
similarity index 100%
rename from building.mdwn
rename to building.md

diff --git a/checking.mdwn b/checking.md
similarity index 100%
rename from checking.mdwn
rename to checking.md

diff --git a/env.mdwn b/env.md
similarity index 100%
rename from env.mdwn
rename to env.md

diff --git a/index.mdwn b/index.md
similarity index 100%
rename from index.mdwn
rename to index.md

diff --git a/leap.mdwn b/leap.md
similarity index 100%
rename from leap.mdwn
rename to leap.md

diff --git a/python.mdwn b/python.md
similarity index 100%
rename from python.mdwn
rename to python.md

diff --git a/references.mdwn b/references.md
similarity index 100%
rename from references.mdwn
rename to references.md

diff --git a/repositories.mdwn b/repositories.md
similarity index 100%
rename from repositories.mdwn
rename to repositories.md

diff --git a/ruby.mdwn b/ruby.md
similarity index 100%
rename from ruby.mdwn
rename to ruby.md

diff --git a/todo.mdwn b/todo.md
similarity index 100%
rename from todo.mdwn
rename to todo.md