Added Clang Format File

Added .clang-format to specify the code format for the project.
It relies on the tool clang-format. clang-format is not shipped
in xcode command line tools. To use clang-format inside xcode
download and install clangformat-xcode
https://github.com/travisjeffery/ClangFormat-Xcode
Merge pull request #29 from cloudant/clang_formatter

Added Clang Format File