Install using 'install' instead of 'cp'. Install 'todo.sh' instead of 'todo'
Allow the use of global config file

If not found elsewhere, look for the config file in /etc/todo/config.
`make install` installs a global config file, setting TODO_DIR=~/.todo.
todo.sh creates TODO_DIR if it doesn't exist.
ENH: Allow configuring null data files and then don't create them.

Request from exatto (http://article.gmane.org/gmane.comp.diary.todotxt/4699), who doesn't want to use done.txt and report.txt.

Also consider character devices (-c; /dev/null is one) in the file existence checks so that no empty file is then created.
Simplify empty data file creation.

No need to use the external cp command; shell redirection will create an
empty file for us.
Fix changelog link in readme
Merge pull request #117 from pdclark/master

Fix changelog link in readme
Merge pull request #116 from inkarkat/enh-allow-null-files

Allow configuring null data files and then don't create them.
Add .travis.yml

`make dist && sudo make install` are used
to install to /usr/local. `make test` then
verifies the changes.
Add Build Status to README
Merge pull request #123 from joshmoore/24pr-travis-yml

Enable Travis-CI
Update build status
Merge pull request #111 from mgarrido/global_opts

Allow the use of a global config file
Allow coloring contexts and projects independently

Because @contexts and +projects are metadata as much as they are text,
it can be nice to highlight them independently of the coloring of the line
that contains them.  This is tough to do correctly in
a TODOTXT_FINAL_FILTER because doing it at that layer requires
re-parsing the text of the line to find the appropriate PRI_$x color to
reset to after coloring the word, or trying to reverse engineer where
the color codes inserted by todo.sh end and the user's text begins (and
vice versa).

Closes #119
Allow for placing addons in subfolders.

Addons can be placed in subfolders with the same name as the action,
in order to be able to e.g. clone git repos into the TODO_ACTIONS_DIR
rather than having to download addons and manage updates manually.

Closes #120
Add new config vars enabled in 07b50a07e0007ac43327d31568b5a7cc26f3e0f2