[ctest] Add ctest continuous integration script for unix

Use with ctest [-V] -S.unix.ctest
[travis] remove old and obsolete travis file for osx [ci skip]
Merge pull request #90 from balint42/master

updated "contributing" doc
Merge pull request #98 from jgrewe/master

Getter of optional fields return boost::optionals
Closes #86 

Looks good to me!
Merge pull request #99 from balint42/master

removed "findEntities", completed use of "getEntities" & removed "children" methods
Merge branch 'master' of https://github.com/jgrewe/pandora-1
Implemented "method(const none_t t)" pattern for all instances in "DataArray"
Implemented "method(const none_t t)" pattern for all instances in "DataTag", removed "remove*" methods
Corrected use of "method(const none_t t)" in "DataArray" to only exist for really optional types
Implemented "method(const none_t t)" pattern for all instances in "Dimensions"
Corrected errors in 'Dimensions' and 'DataTag'
Implemented "method(const none_t t)" pattern for all instances in "Properties"
Implemented "method(const none_t t)" pattern for all instances in "Sections"
Implemented "method(const none_t t)" pattern for all instances in "SimpleTag"
DataArray: add getDataExtent method

IDataArray already had the method but it was not exposed in the
DataArray
[test] DataArray: test for correct DataSet extent
DataArray: move the setDataExtent to have *Extent() grouped

No logic changes, just cosmetic.
Merge pull request #105 from gicmo/getDataExtent

Add DataArray::getDataExtent and test it
Merge branch 'master' of https://github.com/G-Node/pandora
new tree_depth method in Section that gives the maximum levels below a
section