add .clangformat

contrib/.clangformat

@@ -0,0 +1,56 @@
+---
+AccessModifierOffset: '0'
+AlignEscapedNewlinesLeft: 'false'
+AlignTrailingComments: 'true'
+AllowAllParametersOfDeclarationOnNextLine: 'false'
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: 'true'
+AllowShortLoopsOnASingleLine: 'true'
+AlwaysBreakBeforeMultilineStrings: 'false'
+AlwaysBreakTemplateDeclarations: 'true'
+BinPackArguments: 'false'
+BinPackParameters: 'false'
+BraceWrapping:
+  AfterClass:      true
+  AfterControlStatement: true
+  AfterEnum:       true
+  AfterFunction:   true
+  AfterNamespace:  false
+  AfterObjCDeclaration: true
+  AfterStruct:     true
+  AfterUnion:      true
+  BeforeCatch:     true
+  BeforeElse:      true
+  IndentBraces:    false
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Custom
+BreakBeforeTernaryOperators: 'false'
+BreakConstructorInitializers: AfterColon
+BreakStringLiterals: 'false'
+ColumnLimit: '0'
+CompactNamespaces: 'false'
+ConstructorInitializerAllOnOneLineOrOnePerLine: 'true'
+ConstructorInitializerIndentWidth: '4'
+ContinuationIndentWidth: '4'
+FixNamespaceComments: 'true'
+IndentCaseLabels: 'false'
+IndentWidth: '4'
+Language: Cpp
+MaxEmptyLinesToKeep: '2'
+NamespaceIndentation: None
+PointerAlignment: Left
+ReflowComments: 'true'
+SpaceAfterCStyleCast: 'false'
+SpaceBeforeAssignmentOperators: 'true'
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: 'false'
+SpacesInAngles: 'false'
+SpacesInCStyleCastParentheses: 'false'
+SpacesInContainerLiterals: 'false'
+SpacesInParentheses: 'false'
+SpacesInSquareBrackets: 'false'
+Standard: Cpp11
+TabWidth: '4'
+UseTab: ForIndentation
+
+...