You could do this with Easy Columns. To get rid of the gap, just go to Settings > Easy Columns and edit the options to change the margins to "0px". However, that'll affect any column created with the plugin sitewide. It may be better to add some CSS to the site like:
margin: 0px !important;
Then when you create the columns, add that class to the column like so:
[ezcol_1half class="gallery"]content here[ezcol_1half class="gallery"]
I'm working on a newer version that'll let you bulk set classes to columns, as well as pick from several styles.