perf improvements to Similarity family
only transform landmarks if they exist
correct SDM tests for numerical instability
Merge pull request #397 from jabooth/fastproc

Performance improvements for Similarity family
Unified fast copying for Menpo
fix landmark tests
remove deepcopy's and warnings
add ImageFeatures reestablishment after copy
slightly clearer Copyable debug code
improve documentation
add Copyable to API docs
copy for pwa
Merge pull request #398 from jabooth/menpocopy

Copyable - fast robust copy() throughout Menpo.