Fixed Bug when selecting Inside Tag

The 'It' text object uses shrink to drop whitespace. However, shrink
expects the delimiters to exist, which are dropped by dropt. This causes
an additional character to be dropped left and right.
vIt selects bcd in <a>abcde</a> instead of abcde. The solution is to not
drop the delimiters in dropt so that they can be dropped by shrink
instead. As this breaks 'it', we have to call drop after dropt to drop
the delimiters there.
Fixed typo
Add test for inside tag It
Rename dropt to innert, update comment
Update version to 0.2.4
Merge pull request #74 from wellle/73-inside-tags

73 Fix inside tags It