travis: install clang-format on Linux
Merge pull request #27 from toxeus/installClangFormat

travis: install clang-format on Linux
style: replace each tab with 4 spaces

Command used:
     sed -ir 's/\t/    /g' "$file"
clang-format: generate initial config

The configuration file was geneated (based on LLVM style)
by using the following command with clang-format 3.4:

    clang-format -dump-config > .clang-format
clang-format: adapt config to Monetas coding style
style: reformat code with clang-format
travis: add clang-format support