gitignore: clean up

This removes several outdated or unnecessary ignore patterns.
Especially those that match random words such as 'local' or 'core',
which repeatedly caused weird behavior that's hard to debug, e.g.
invisble vendored files.

.gitignore

@@ -1,16 +1,10 @@
 *#
-*.[568ao]
-*.a[568o]
-*.cgo*.c
-*.cgo*.go
+.#*
+*-stamp
 /*.yaml
 /*.yml
 /*.rules
 *.exe
-*.orig
-*.pyc
-*.rej
-*.so
 
 # Editor files #
 ################
@@ -20,12 +14,6 @@
 *.iml
 .idea
 
-.DS_Store
-.nfs.*
-[568a].out
-core
-
-*-stamp
 /prometheus
 /promtool
 benchmark.txt
@@ -34,12 +22,6 @@ benchmark.txt
 /.release
 /.tarballs
 
-.#*
-command-line-arguments.test
-*BACKUP*
-*LOCAL*
-*REMOTE*
-
 !/circle.yml
 !/.travis.yml
 !/.promu.yml