[boost] TravisCI and Coveralls integration instructions

Hi all, The following step by step instruction https://svn.boost.org/trac/boost/wiki/TravisCoverals may be useful for those of you who want to: * make sure that tests cover all the code lines * make the README.md more colorful and useful * use additional testing infrastructure Here are some examples of how the results looks like: * https://github.com/boostorg/variant#test-results * https://github.com/boostorg/type_index#test-results P.S.: Shall I add this tutorial to "Guidelines" or to the "Infrastructure" section of the Wiki? -- Best regards, Antony Polukhin