fix typos

docs/source/config_files.rst

@@ -122,7 +122,7 @@ their demo for binder <https://github.com/jupyterlab/jupyterlab-demo/blob/master
 .. _start:
 
 ``start``
-^^^^^^^^^^^^^
+^^^^^^^^^
 
 A script that can contain arbitrary commands to be run at runtime (as an
 `ENTRYPOINT <https://docs.docker.com/engine/reference/builder/#entrypoint>`

docs/source/dev_newbuildpack.md

@@ -23,4 +23,4 @@ Note that this doesn't apply to adding additional libraries / UI to existing
 buildpacks. For example, if we had an R buildpack and it supported IRKernel,
 it is much easier to
 just support RStudio / Shiny with it, since those are library additions than entirely
-new buildpacks.
+new buildpacks.

repo2docker/buildpacks/base.py

@@ -305,7 +305,7 @@ class BuildPack:
         applied at runtime (set environment variables).
 
         The scripts should be as deterministic as possible - running it twice
-        should not produce different results.!
+        should not produce different results.
 
         """
         return []