* add mutex to avoid crash on qhash data update (#62)

* update gitignore
* update contributing.md

.gitignore

@@ -1,7 +1,49 @@
-sources/build
-sources/usr
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+# cmake
+CMakeCache.txt
+CMakeFiles
+CMakeScripts
+Makefile
+cmake_install.cmake
+install_manifest.txt
+
+# build directory
+build
+
+# archives
 *src.tar.[gx]z
 *pkg.tar.[gx]z
-build
 src
 pkg
+
+# idea
+.idea
+