using fixed size Eigen head(), tail() and segment()
Vector::segment() can now use variable starting index
added testing versions of dynamic head and tail functions
added get/set-head/tail/segment to Vector class for dynamic and static sized vectors
Merge pull request #13 from ethz-asl/develop

Extended vector class
Improved doc of RotationMatrix
vector constructors can now take other vectors of any type. dynamic sized constructor now working
Merge pull request #14 from ethz-asl/develop

vector constructors can now take other vectors of any type. dynamic sized constructor now working
Merge branch 'origin/master'