Raise if lookup_for target does not use lookup_by

The previous behavior was just to let a NoMethodError bubble up in
response to calling #lookup on the constantized class name.
add lookup.seed(*values) method to seed tables
version 0.5.0
Merge pull request #10 from pd/more_helpful_lookup_for_error

Raise if lookup_for target does not use lookup_by
v0.6.0
stop building rbx on travis.yml
rspec 3 support

* rewrite use of "its" as regular "it" assertions as "its" is no longer part of rspec-core
* change "be_true" assertions to use "be true" since True no longer responds to true?
* sneak in require of pry in spec helper
add rspec-its gem
Merge pull request #13 from spacechurro/rspec_its

support for rspec 3
raise if cache: true and find_or_create: true
v0.7.0
Implement `lookup_by :foo, raise: true` to raise on miss

Closes #14.
Fully convert to rspec3's expect() syntax

Mostly performed using the yujinakayama/transpec tool, with minor manual
tweaking for readability.
Support `fit` by defaulting to filter on `:focus`
Appraisals over rails 3.2.x, 4.0.x, 4.1.x
Run appraisal on travis
Add `raise: true` to the README
LRU#merge! should return self

The spec around `LRU#merge` was also simply wrong -- with an LRU size of
2, once we merge 2 keys in, one has to be thrown away.

Rubinius was actually *right*; I needed to reimplement `merge` in the
obvious manner to fix MRI.
Rails 3.2.x compatibility fixes

For UUIDs, the base type of the column is `:string`, not `:uuid`.

For `smallint` support, Rails 3.2.x is not raising `StatementInvalid` in
response to the `PG::NumericValueOutOfRange` that the PG gem should be
raising; it seems to swallow the error, or not use the value in the
first place. So just assert the `sql_type` rather than `create()` failing.
Merge pull request #15 from pd/raise-on-miss

Implement `lookup_by :foo, raise: true` to raise on miss