README.md: Revise language and formatting

Author: msabramo

README.md

@@ -1,12 +1,15 @@
-Tup - http://gittup.org/tup
-
-About Tup
--------------------------------------------------------------------------------
-Tup is a file-based build system for Linux, OSX, and Windows. It inputs
-a list of file changes and a directed acyclic graph (DAG), then processes
-the DAG to execute the appropriate commands required to update dependent
-files. Updates are performed with very little overhead since tup implements
-powerful build algorithms to avoid doing unnecessary work. This means you
-can stay focused on your project rather than on your build system.
-
-Further information is found at http://gittup.org/tup
+# Tup
+
+http://gittup.org/tup
+
+## About Tup
+
+Tup is a file-based build system for Linux, OSX, and Windows. It takes
+as input a list of file changes and a directed acyclic graph (DAG). It
+then processes the DAG to execute the appropriate commands required to
+update dependent files. Updates are performed with very little overhead
+since tup implements powerful build algorithms to avoid doing
+unnecessary work. This means you can stay focused on your project rather
+than on your build system.
+
+Further information can be found at http://gittup.org/tup