starts refactoring according to #34
breaks down code
fixes png encoding bug
closes #34. progress with #28
fixes travis build failure
fixes travis build failure
fixes build on windows

different compilers have different levels of strictness. for now, link
all dependencies to both encoder and decoder. in the future, find a way
to remove unnecessary dependencies.
implements resize worker (progress #28)
implements rotate worker (progress #28)
implements blur worker (progress #28)
implements crop worker (progress #28)
implements mirror worker (progress #28)
implements pad worker. tweaks rotate. progress #28
eases the stress tests. tweaks LwipImage class.
closes #28 (node 0.11 support)
Merge pull request #37 from EyalAr/nan_ref

Node 0.10 & 0.11 compatibility