opentelemetry 1.0.0beta7

opentelemetry 1.0.0beta7
* adding more tests (#82)
* disabling expanding args for internal functions (#84)
* check for invalid hook function signatures (#79)
* adding checks for conflicting extensions (#83)
* adding notes and minor code improvements for issue 68 (#75)
* fixing crash + docs (#76)
* fixing clang-format install (#78)
* adding valgrind (#73)
* fixing segfault when returning params from pre callback (#72)
* adding failing tests for pre-hook params (#71)
* moving docs back to root (#70)
* add failing test for expand params with post callback (#69)
* moving extension to subdirectory (#65)