Issue #25: fix bootstrap.sh to work for RHEL7

- RHEL no longer has an optional channel, so
we remove the section which subscribes to the
optional repo
- Pipe out epel repo config with generic url
so that the latest epel-release is always
installed, then enable the epel repo
- Move python-kid download and install after
the epel repo enable
- Install packages which are not included in
the default RHEL build (now installable via
yum install because epel repo is enabled)