Fix .gitignore patterns

Fixes #110 on Github. As the issue describes, `**` is not
the right syntax.

We could write `**/*.pyc` instead, but according to
https://git-scm.com/docs/gitignore a pattern already
matches at any directory level if it doesn't contain `/`.

Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

.gitignore

@@ -5,18 +5,18 @@
 #
 
 # generated python bytecode
-**.pyc
+*.pyc
 
 # latex generated files
-**.aux
-**.log
-**.out
-**.lof
-**.lot
-**.bbl
-**.blg
-**.toc
-**.mpx
+*.aux
+*.log
+*.out
+*.lof
+*.lot
+*.bbl
+*.blg
+*.toc
+*.mpx
 
 tools/parsetab.py
 manual/env.tex