Enable version discovery from tarball directory; remove spurious git.version file.

Currently, "./configure; make install" picks up the hard-coded version in the git.version file.  Removing that file, though, requires that a .git directory be present (i.e. that the installation be from a clone, rather than a tarball).  This change enables installation from a tarball, as long as the tarball's directory is named using the version number (which is the case for github.com/.../eups/archive/$VERSION.tar.gz URLs).