Move include/utilities/*.h to include/rocksdb/utilities/*.h

Summary:
All public headers need to be under `include/rocksdb` directory. Otherwise, clients include our header files like this:

    #include <rocksdb/db.h>
    #include <utilities/backupable_db.h> // still our public header!

Also, internally, we include:

    #include "utilities/backupable/backupable_db.h" // internal header
    #include "utilities/backupable_db.h" // public header

which is confusing.

This way, when we install rocksdb as a system library, we can just copy `include/rocksdb` directory to system's header files. We can't really copy `utilities` directory to system's header files.

Test Plan: compiles

Reviewers: dhruba, ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20409
Bump the version
Also bump version in Makefile
Fixed a bug in Compaction.cc where input_levels_ was not properly resized.

Summary:
Fixed a bug in Compaction.cc where input_levels_ was not properly resized.
Without this fix, there would be invalid access in input_levels_ when more
than two levels are involved in one compaction run.

This fix will go to master instead of compaction branch.

Test Plan: tested in compaction branch.

Reviewers: ljin, sdong, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20481
Fixed a compile error in util/options_builder.cc

Summary:
Fixed the following compile error by replacing pow by shift, as it computes
power of 2.

util/options_builder.cc:133:14: error: no member named 'pow' in namespace 'std'
        std::pow(2, std::max(0, std::min(3, level0_stop_writes_trigger -
        ~~~~~^
1 error generated.
make: *** [util/options_builder.o] Error 1

Test Plan: make success in mac and linux

Reviewers: ljin, igor, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20475
Merge branch 'master' of https://github.com/facebook/rocksdb