Update libmagick references to the C library

Explicit cast of size_t to 32 bit integer

Ensures compilation with nan 1.5.0+

Version bumps

Version bumps

Correct location of Dockerfile

Minimum version of libvips now 7.40.0 lovell#74

Prevent auto-rotate fail for libmagick formats lovell#117

Version bumps ahead of v0.7.1

Code lint of new features

Improve Stream error handling lovell#88