Record files don't always include directories so find eggdir by looking for a file within it.

Fixes #2075
Better detection of egg-info dirs
Merge pull request #2076 from abadger/feature/no-egg-info-dir-in-record

Record files don't always include directories so find eggdir by looking ...
Update changelog to include PR #2076
.gitignore: add .sw[a-z] files

for ViM swap files
unpack_url: session only needed for unpack_http_url
vcs: add documentation to VersionControl class
cleanup: use "with open()" to open files
freeze: simplify code and use with open()