Update getting-started.rst to fix broken link

fixes broken link to introduction.html

docs/getting-started.rst

@@ -5,7 +5,7 @@ As a general purpose blockchain engine, Tendermint is agnostic to the
 application you want to run. So, to run a complete blockchain that does
 something useful, you must start two programs: one is Tendermint Core,
 the other is your application, which can be written in any programming
-language. Recall from `the intro to ABCI <introduction.rst#ABCI-Overview>`__ that
+language. Recall from `the intro to ABCI <introduction.html#ABCI-Overview>`__ that
 Tendermint Core handles all the p2p and consensus stuff, and just
 forwards transactions to the application when they need to be validated,
 or when they're ready to be committed to a block.