Changed push.default from `simple` to `matching`.

Version of Git on servers is behind the times (1.7.x) and doesn't yet
support a push.default setting of `simple`.
Refactored bashrc for multiple operating systems.

Created three bashrc files: one each for Mac OS, SunOS, and Linux. These
are sourced from primary `.bashrc` file based on the operating system of
the local machine.

Moved all aliases into bash_aliases.