Reference markdown file for in-site links

Author: afh

source/contribute.md

@@ -22,7 +22,7 @@ Please report bugs at the [GitHub issue page](https://github.com/ledger/ledger/i
 The [ledger source code](https://git.ledger-cli.org/ledger) is available on GitHub, contributions welcome!
 
 **Website**
-[About ledger-cli.org](about.html) documents this site so you can help improve it.
+[About ledger-cli.org](about.md) documents this site so you can help improve it.
 
 **Twitter**
 [#ledgercli](https://twitter.com/search?q=%23ledgercli&src=typd&f=realtime) Ledger-related tweets

source/features.md

@@ -43,4 +43,4 @@ accounting systems include:
   check account balances, reconcile accounts, keep track of capital
   gains on stocks, etc.
 
-Read the [docs](docs.html) to learn more.
+Read the [docs](docs.md) to learn more.

source/index.md

@@ -35,4 +35,4 @@ $ ledger -f example.dat register Expenses
 15-Oct-12 Exxon               Expenses:Auto:Gas          $10.00      $10.00
 ```
 
-Read more about Ledger's [features](features.html).
+Read more about Ledger's [features](features.md).