Fix deprecations on OSX and linux

v0.4.1

Add the 4 basic operations to GRDgrid types.

Julia 0.7 ready

Drop support to Julia versions prior to 0.7

Solve issues with Julia version require

v0.3.0

Expand a little about some options in the examples.

Fix issue with GMT.jl file not exporting some correct function names

v0.2.1

Swap to 5

Add a By module name upper lever interface

v0.2.0

Add GMT description

No longer 0.4 and no need for Compat

v0.1.0

Remove left over Compat calls.

Sync with latest GMT5.4 changes

Sync with GMT_PALETTE struct changes in GMT5.4

Fixes and updates to keep in sync with GMT lib updates

It is now possible to call GMT with gmt("module","options",data)