Add autoenv_run() for manually executing files

When running autoenv_check_authz_and_run from command lines there are two
obvious problems:

 1. The command is ugly
 2. It does not expect to find a relative path and adds a relative path to the
    auth file

I am using this new command inside my .env file to differentiate between global
and local environment settings. Now I can upload my .env into Git while my
passwords and environment-local settings (eg. PATH) will be hooked from my
`.local` file. This is my example .env:

    use_env killer_app
    export DATABASE_URL='postgres://root@localhost'

    SCRIPT_DIR=$(builtin cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd)
    LOCAL_FILE="$SCRIPT_DIR/.local"
    if [ -f $LOCAL_FILE -a ! -z $AUTOENV_AUTH_FILE ]; then
        autoenv_run "$LOCAL_FILE"
    fi

This provides some additional security when collaborating with others and
sharing some environment defaults needed by a 12 factor app.
Merge pull request #44 from ferrix/autoenv_run

Add autoenv_run() for manually executing files
Typo fix
Merge pull request #46 from frankshearar/master

Typo fix.
Handle the case where grep is an alias to egrep same way as autoenv_check_authz() do.

egrep -G (grep -EG) results in conflicting matchers
Export all variables in an .env file, actually Foreman-compatible now

Closes #38.
Merge pull request #49 from devinus/master

Export all variables in an .env file, actually Foreman-compatible now
Fix shasum not being available on all distros. Fixes #23

Changed shasum to sha1sum.
Update README.rst
Merge pull request #47 from z4y4ts/patch-1

Handle the case where grep is an alias to egrep same way as autoenv_check_authz() do
Should now work under OS X
Merge pull request #55 from mahmoudhossam/patch-1

Fixed problem with OS X not having sha1sum
Change check for shasum

shasum wasn't getting found on OS X 10.9.1 with zsh 5.0.5
Update README.rst with required Mac Homebrew step

After googling to https://github.com/kennethreitz/autoenv/issues/41 and https://github.com/kennethreitz/autoenv/pull/51 I finally did this to make autoenv work.
Merge pull request #60 from groovecoder/master

Update README.rst with required Mac Homebrew step
Merge pull request #58 from unixorn/master

Change check for shasum
Merge remote-tracking branch 'upstream/master'