Fixed gitignore for pdf

.gitignore

@@ -31,12 +31,6 @@ MANIFEST
 *.synctex.gz
 *.sh
 
-# TeX exceptions
-!/tex/**/*.png
-
-# published article exception
-!article_published.pdf
-
 # Generated results from FEniCS/Python plots, etc...
 *.xdmf
 *.h5
@@ -52,14 +46,14 @@ tests/
 # Paraview state files
 *.pvsm
 
-*.aux
-*.log
-*.pdf
-*.synctex.gz
-*.sh
-
-# Submission 1
+# Submission
 **/*.synctex.gz
 **/*.log
 **/*.aux
-**/*.pdf
+**/*.pdf
+
+# published article exception and
+# TeX exceptions
+!/tex/**/*.png
+!article_published.pdf
+!conferences/