Minor fixes (#93)

* Run Maven workflow only on source changes.

* Fix link.

Author: aaronbembenek

.github/workflows/maven.yml

@@ -10,9 +10,11 @@ name: Java CI with Maven
 
 on:
   push:
-    branches: [ "master" ]
+    branches: ["master"]
+    paths: ["src/**"]
   pull_request:
-    branches: [ "master" ]
+    branches: ["master"]
+    paths: ["src/**"]
 
 jobs:
   build:

docs/lang_ref/index.md

@@ -9,4 +9,4 @@ nav_order: 5
 This set of documents describes the Formulog language (as opposed to its current implementation).
 Please raise a [GitHub issue](https://github.com/HarvardPL/formulog/issues/new) if anything is unclear, incomplete, or incorrect :)
 
-For an overview of Formulog and its motivations, we recommend checking out our [publications]({{ site.baseurl }}{% link pubs.md %}).
+For an overview of Formulog and its motivations, we recommend checking out our [publications]({{ site.base_url }}{% link pubs.md %}).