tp.h: fix buffer allocation supporting any writer
https://github.com/mailru/tarantool/issues/20
tp.h: tp_select example correction.
tp.h: test fixed and refactored.
When loading data from a snapshot, validate tuples

Don't load corrupted tuples.
Merge branch 'stable' of github.com:mailru/tarantool into stable
Merge branch 'stable'

Conflicts:
	.gitignore
	include/pickle.h
	test/unit/CMakeLists.txt
	third_party/luajit