Improve error message for selecting into slice.

If user passes a type of []*Struct instead of *[]*Struct, tell them so.

Tested by changing this line in gorp_test.go:

       var puArr []*PersistentUser
       _, err = dbmap.Select(&puArr, "select * from PersistentUser")

to

	var puArr []*PersistentUser
	_, err = dbmap.Select(puArr, "select * from PersistentUser")

and observing this error message on test failure:

	panic: gorp: Cannot SELECT into a non-pointer slice: []*gorp_test.PersistentUser
#48 add stmt.Close() to Transaction.Exec to avoid memory leak on postgres
Merge pull request #47 from robfig/master

Improve error message when user attempts to select into a non-pointer slice.
#46 add example of selecting into slice of pointers.  clean up README quite a bit.  Add Rob and Quinn to contributors.
#44 - support uint primary key types
#44 - add assertions on post-insert bound Id field
pq repo moved

now at github.com/lib/pq
Merge pull request #50 from ottob/pq_repo_moved

pq repo moved
Panic when the user requests an auto-inc pkey.

Setting auto-increment for a multi-column primary key presently fails
silently; this makes it fail loudly.

A better fix would be to figure out where/why the silent failure occurs.
Merge pull request #51 from bensigelman/master

Panic when the user requests an auto-inc pkey with multiple cols
Add doc comment about panic().  Modify panic to occur if isAutoIncr and len(fieldNames) != 1
#49 - add dbmap.DropTablesIfExists method
Merge branch 'master' of github.com:coopernurse/gorp