Add note to .gitignore on how to ignore locally-specific files

Also, this removes a couple locally-specific files I had previously added.

Change-Id: Ib93e0dc5aeb062321e47f77a084b0581f87046c6
Reviewed-on: https://code.wireshark.org/review/315
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Evan Huus <eapache@gmail.com>

.gitignore

@@ -1,3 +1,13 @@
+#
+# This file is tracked by git for the wireshark repository, and thus
+# should only contain ignore entries common to all wireshark developers.
+# To ignore files specific to your local repository, for example files
+# generated by your editor, add them to your repository exclude file
+# (.git/info/exclude) or your global ~/.gitignore_global. For details
+# see:
+#   https://help.github.com/articles/ignoring-files
+#
+
 # Compiled or generated source #
 ################################
 *.dll
@@ -9,6 +19,7 @@
 *.pyc
 *.so*
 *.[oa]
+*.dylib
 *grammar.out
 *grammar.[ch]
 *scanner.c
@@ -189,6 +200,3 @@ packaging/macosx/Wireshark_package.pmdoc/index.xml
 packaging/rpm/SPECS/wireshark.spec
 packaging/svr4/checkinstall
 packaging/svr4/pkginfo
-*.dylib
-*.sublime-project
-*.sublime-workspace