Making sure errors don't halt the import.

Wrapped file operations in a begin/rescue block.
Convert slashes in titles to dashes when migrating from WordPress

When a post has a title that contains a slash, such as 'This is my cool
blog post part 1/2', convert the slash to a dash so that the post
filename is created correctly.

Fixes issue #680
Merge branch 'master' of git://github.com/mojombo/jekyll
Remove the coverage rake task

RCov does not work on Ruby 1.9.x
Add simplecov as a dependency

Simplecov works with Ruby 1.9.x for generating test coverage
Add SimpleCov to the unit tests
add the coverage directory to .gitignore
filter out test files in coverage results
Merge pull request #765 from mattr-/fix-coverage

Fix coverage
Update history to reflect merge of #765.
Refine CONTRIBUTE with more detail and better formatting.
Merge pull request #671 from fzero/master

Rescue from import errors on Wordpress.com plugin.
Printing error message in WP.com migrator. #671.
Reflected merging of #671 in History.
Merge pull request #684 from mattr-/issue-680.
Added note in gemspec for easy extraction of dev dependencies to migrator gem.