v0.1.4: Add submodule FEMBase.Test (#19)

Module can be used to test extensions.

New types

• LinearSystem to hold all matrices using buildin Julia types
• AbstractLinearSystemSolver to implement solvers to solve LinearSystem
• AbstractAnalysis to implement new analyses, e.g. static, dynamic, modal, buckling etc. analysis

v0.1.2: New feature for update!-function (#11)

It's possible to replace or add new field to element using command

```julia
f = field(1)
update!(element, "my field", f)
```

v0.1.1: Minor fixes (#9)

* export get_reference_element_coordinates
* refactor assembly.jl
* refactor fields.jl, implement == to compare fields
* use add! instead of push! to add single entry for sparse matrix
* test comparison of fields, simplified creating of DVTI
* assemble.jl: test creating new problems
* fixed deprecated syntax, remains backward compatible to JuliaFEM.

v0.1.0: Bugfixes and changes (#3)

Added some missing functions and fixed bugs so that JuliaFEM.jl tests
pass now. Minor changes to `fields.jl` break backward compatibility, changing new minor version.

Refactor + documentation

Refactor and document fields.jl (#2)

Code for working with fields is now refactored and documented. A slight modification is done how to define variable fields. Earlier the syntax was to define a vector with some content, but this syntax was not unambiguous, e.g. 

```julia
el = Element(Seg2, [1,2])
update!(el, "f", [1.0, 2.0])
```

could mean either constant vector field or variable scalar field in case of Seg2. Now variable field is defined using Tuple so it's always clear what kind of field is defined. So the new syntax for declaring constant vector field or variable scalar field goes

```julia
el = Element(Seg2, [1,2])
update!(el, "constant vector field", [1.0, 2.0])
update!(el, "variable scalar field", (1.0, 2.0))
```

Test coverage to 100 %

Now full test coverage. Next step: code refactoring + api documentation.