Updated the fetcher subprocess to pass in the environment explicitly.

Review: https://reviews.apache.org/r/19164
Fixed a call to delete where delete[] should have been used.
Added support for constructing a Future from a Try.

Review: https://reviews.apache.org/r/20106
Added 'make bench' make target to run benchmark tests under 'src/'.

- The 'benchmark' tests are the GTEST test cases or tests with the name containing 'BENCHMARK_'.
- The tests can be inovked by 'make bench' command or 'make check' with a non-zero environment variable MESOS_RUN_BENCHMARKS value.

Review: https://reviews.apache.org/r/20017
Added JobServer to the list of job schedulers that are implemented as Mesos
Framework.

This closes #13.

Review: https://github.com/apache/mesos/pull/13
Added link to Javadoc and reorganized framework developer links.

Review: https://reviews.apache.org/r/20004
Used implicit Try -> Future flattening in the Slave.

Review: https://reviews.apache.org/r/20178
Undid the line wrapping for email template in release script.
Made os::system async signal safe.

Review: https://reviews.apache.org/r/20127
Added a few methods for net::MAC and net::IP.

Review: https://reviews.apache.org/r/19982
Updates download version listed in Getting Started guide to 0.18.0
Fixed process::await and process::collect to take const references.

Review: https://reviews.apache.org/r/20231
Added a metrics API.

Review: https://reviews.apache.org/r/18718
Removed timeouts in interfaces in favor of Future::after.

Review: https://reviews.apache.org/r/19672
Used Future::after in Network.

Review: https://reviews.apache.org/r/19674
Cleaned up master detector usage in tests.

Review: https://reviews.apache.org/r/19834
Refactored State::names to return a set instead of vector.

Review: https://reviews.apache.org/r/19835
Added log implementation for state storage.

Review: https://reviews.apache.org/r/19007
Updated protobuf::read to support reading from pipe, socket or FIFO.

Updates stout's protobuf::read by introducing the "undoFailed" flag
which should be set towards false (default) on file descriptors that
are connected to a pipe, socket or FIFO. This flag may be set towards
true on file descriptors supporting random access, enabling seek
position reverting (aka undoing) on failed read attempts.

Review: https://reviews.apache.org/r/20216
Updated uses of protobuf::read towards explicit undo where needed.

Review: https://reviews.apache.org/r/20237