added space after a md formatted link

bad: [my link](http://my.link.com): blahblah
good: [my link](http://my.link.com) : blahblah

bad: [my link](http://my.link.com)! blahblah
good: [my link](http://my.link.com) ! blahblah

without the space, url_checker_pwl.pl will get confused
Merge pull request #129 from borgified/small_format_changes

added space after a md formatted link
Fix up for missing link.
Create event-calculus.txt
Merge pull request #131 from chrisamaphone/master

Added Event Calculus paper
added Organizing Programs Without Classes and updated README
Update README.md

Add Gittip widget.
Update README.md
Merge pull request #133 from DarrenN/organizing-programs-without-classes

Added Organizing Programs Without Classes and updated README
Updated README
Create README.md
Create README.md
Create README.md
Added headling
Update headline
Update README.md
Update README.md
Merge pull request #135 from DarrenN/apis

Updated README for api_design
Update README.md
Update README.md