util: initialise the rng inside a std::call_once

This makes it threadsafe.
util: explicitly cast to unsigned int when initialising the rng

Closes issue #77
Merge pull request #79 from gicmo/win_rand

Looks all OK
Merge pull request #75 from balint42/master

Implemented new getMultiple pattern for all instances in Block

This was quite allot: thanks. 
As far as I can tell everything is OK.
[travis] Use ctest for building the project

Using ctest for everything has the advantage that the all the
individual steps (configure, build, test) will be submitted to the
dashboard, including all the warnings generated in all steps
[cdash] change project name to nix
[travis] Silence unused arguments warning for clang

Happens during linking, but we are not interested in it.
[travis] Use COMMIT instead of BRANCH for build name
[cdash] shorten commit id in build name to 7 chars

And remove "travis" from build name (that is clear from the site).
[cdash] attach travis configuration to the submission
[travis] enable irc notifications
Merge pull request #80 from gicmo/travis_ctest

[travis enhancements] Use ctest for building the project
[travis] enable static analysis via clang-check
Merge pull request #81 from balint42/master

Implemented new abstract pattern for "find*" methods using a "findEntities"
Merge pull request #82 from gicmo/static_analysis

[travis] enable static analysis via clang-check
first version of contribution guidelines.
Merge pull request #85 from jgrewe/master

first version of contribution guidelines.
[cdash] move to own site (crash.0xdeadbabe.info)
updated "contributing" doc