Update kerl to grok KERL_INSTALL_MANPAGES env

The KERL_INSTALL_MANPAGES is ignored if given in the environment. Fixing that by saving and restoring the KERL_INSTALL_MANPAGES along the rest of the options.

By the way, KERL_INSTALL_HTMLDOCS is not reset in the beginning of the file, so no save/restore is necessary for it.

Though its an inconsistency due to be fixed... as a separate ticket.
Merge pull request #65 from vlm/patch-1

Update kerl to grok KERL_INSTALL_MANPAGES env
Follow redirects
Support new erlang's release naming convention when we get list of releases
Fix order of sed commands in the pipeline when we return list of releases
We don't need first sed since cut would return lines without delimeter
Fix confusing kerl usage string for `update`

[lwalkin@lwalkin:~]> ./kerl update
usage: ./kerl  <releases>

should be:

[lwalkin@lwalkin:~]> ./kerl update
usage: ./kerl update releases

This patch fixes that.
Make sure final release is after release candidates
Update kerl
Github apparently changed the hostname for downloads
Merge pull request #73 from vlm/patch-1

Fix confusing kerl usage string for `update`
Merge pull request #74 from macintux/jrd-fix-curl

Fix raw path for kerl download
Remove release from otp_builds on 'delete build' in case when build directory is missing
Merge pull request #75 from spawngrid/issue_72

Remove release from otp_builds on 'delete build' in case when build dire...