Enhance clang format (#46)

Approach
What is the motivation for this PR?
Fix current clang-format file:
1. disable includes sorting
2. always put class braces into a new line.

Author: lolyu

.clang-format

@@ -28,10 +28,12 @@ BraceWrapping:
   BeforeCatch: false
   AfterFunction: true
   AfterNamespace: true
+  AfterClass: true
 # no line width limit
 ColumnLimit: 0
 KeepEmptyLinesAtTheStartOfBlocks: true
 SortIncludes: true
 SpacesBeforeTrailingComments: 1
 # always break an open bracket, place closing bracket on a new line
 AlignAfterOpenBracket: BlockIndent
+SortIncludes: false