Problem: inconsistent code style

Solution: copy .clang-format from `libzmq` as a starting point.

There is no need to follow exactly what libzmq does but it seems
reasonable starting point. It would be good to stick to one style as
there is a lot of activity and good ideas lately.

.clang-format

@@ -0,0 +1,53 @@
+BasedOnStyle: LLVM
+IndentWidth: 4
+UseTab: Never
+BreakBeforeBraces: Custom
+BraceWrapping: 
+    AfterClass: true
+    AfterControlStatement: false
+    AfterEnum: true 
+    AfterFunction: true 
+    AfterNamespace: true
+    AfterObjCDeclaration: true 
+    AfterStruct: true 
+    AfterUnion: true 
+    BeforeCatch: true 
+    BeforeElse: false 
+    IndentBraces: false
+
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AllowShortIfStatementsOnASingleLine: false
+IndentCaseLabels: true
+BinPackArguments: true
+BinPackParameters: false
+AlignTrailingComments: true
+AllowShortBlocksOnASingleLine: false
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortFunctionsOnASingleLine: InlineOnly
+AlwaysBreakTemplateDeclarations: false
+ColumnLimit: 80
+MaxEmptyLinesToKeep: 2
+KeepEmptyLinesAtTheStartOfBlocks: false
+ContinuationIndentWidth: 2
+PointerAlignment: Right
+ReflowComments: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: Always
+SpaceInEmptyParentheses: false
+SpacesInAngles: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard: Cpp11
+
+SortIncludes: false
+
+FixNamespaceComments: false
+BreakBeforeBinaryOperators: NonAssignment
+SpaceAfterTemplateKeyword: true
+AlignAfterOpenBracket: Align
+AlignOperands: true
+BreakConstructorInitializers: AfterColon
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+SpaceAfterCStyleCast: true
+BreakBeforeTernaryOperators: true