Added R16B compatibility and missing dependencies.

While installing on Arch Linux, I ran into a lot of issues. This pull requests fixes most of them , hopefully without breaking backward compatibility.

* The C source for `ecoinpool_hash.so` wasn't being compiled when running Erlang R16B. I added that version of Erlang to the version check.
* The C source for `jiffy.so` wasn't building. Since this is a dependency, I updated the README to explain that manually compiling jiffy might be required.
* `ejson` Wasn't part of the dependencies and caused ecoinpool to crash at runtime. I have updated the dependencies to get @benoitc 's version of `ejson`. It is licensed under Apache 2.0 and is thus valid in this project. (See the link in `rebar.config` for compatibility notice.)
* `OTP R16B` deprecates parameterized modules. Ericsson provides an open source module called `parse_transform` which will enable legacy code to run with parameterized module support. I have added that as a dependency and included it in the relevant `.erl` files. This module is supposed to work on older versions of Erlang, but I haven't tested, so you might be interested in trying it out before accepting the pull request.

I think this is pretty much everything.

Cheers