make _get_comp_words_by_ref more strong

Use dot instead of source

Allow env vars to override default values

If using OS X El Capitan, try to add OpenSSL

According to the docs it is possible to configure kerl both by using `.kerlrc`
and passing ENV variables from the command-line, i.e.

    KERL_INSTALL_MANPAGES=yes ./kerl install <build> <path>

However the ENV vars were being cleared/overriden, so you could only use `.kerlrc`.

This fixes it.

In Ubuntu /bin/sh is /bin/dash, which doesn't support the source command.

Build a Dialyzer PLT when installing a build

pcre grep errors fix in mac os