Unwraps for usages that comply with the `netCDF` requirements

Ownership

One can have two VariableMut active, but one can not have
mutable access to the same VariableMut...

Multi-valued attributes

it is safe to read attributes when they are cached, which happens
during the first read of any v...

put_values_strided

add values_strided_to

ignore coverage in the tests

now runs coverage runs on the stable branch

enforce read only access to read only file

Remove indexmap

add set_nofill

use references to traverse tree

One can now traverse upwards in lineage, which makes
keeping track of dimensions and types easier.

add ncdump example application

Add endian support

Add docs and download badges

wrap NC_STRING

travis improvements

Build can fail on nightly.
cargo build, test, bench, doc all launched.

add #[warn(missing_docs)] giving warnings when including an item that is
not documented

Variables can use dimensions from all parents, which might be a
problem if two dimensions share ...

as the dimensions are moved straight into the variable, it makes
more sense to transfer ownership

The root dimensions were not visible in the children due to a
forgotten parameter when parsing t...

Adds a missing constant in the netcdf-sys crate which requires a version
bump

running `tarpaulin` on the codebase reveals a couple of items
that should be tested, and which n...

attributes do not have any methods requiring mutable access

Makes iterating mutably over variables a bit easier, and
hides internal library details. By hidi...