Add a make target to update update the hashes
Better detection of the module to check the hashes
Prepare for CMake 3.0.0 and use FindPkgConfig from cmake master in cmake-next

For now use v3.0.0-rc2 tag.

The FindPkgConfig has been merged with improvements in CMake master,
therefore it is no longer necessary and the git version can be used.
Import Modules/FeatureSummary.cmake from CMake master in cmake-next
Add unit tests for YCMBootstrap
Add unit test to check that sha1sums are correct
Run unit tests in travis-ci