Shopify/identity_cache — pull request #78 by arthurnn (2013-07-16 16:14:20+00:00)
Title: dont memoaize the namespace on the class level

This does not affect much the performance. follow benchmarks

before PR
```ruby
/opt/boxen/rbenv/versions/1.9.3-p385-perf/bin/ruby ./performance/cpu.rb
Rehearsal ----------------------------------------------------
FindRunner: 0.860000 0.090000 0.950000 ( 1.224831)
FetchMissRunner: 12.160000 0.760000 12.920000 ( 83.156324)
FetchHitRunner: 13.250000 0.850000 14.100000 ( 84.238404)
------------------------------------------ total: 27.970000sec

user system total real
FindRunner: 0.840000 0.080000 0.920000 ( 1.190167)
FetchMissRunner: 12.010000 0.730000 12.740000 ( 82.843079)
FetchHitRunner: 13.250000 0.840000 14.090000 ( 84.364599)
```

after PR
```ruby
/opt/boxen/rbenv/versions/1.9.3-p385-perf/bin/ruby ./performance/cpu.rb
Rehearsal ----------------------------------------------------
FindRunner: 0.890000 0.090000 0.980000 ( 1.258933)
FetchMissRunner: 12.580000 0.780000 13.360000 ( 84.006055)
FetchHitRunner: 13.760000 0.890000 14.650000 ( 85.127375)
------------------------------------------ total: 28.990000sec

user system total real
FindRunner: 0.860000 0.080000 0.940000 ( 1.214727)
FetchMissRunner: 12.270000 0.750000 13.020000 ( 82.983523)
FetchHitRunner: 13.810000 0.880000 14.690000 ( 85.356588)
```

cc @camilo @hornairs @dylanahsmith