Set up documentation + lint (#121)

- remove some automatically generated stuff not should even be in
repository
- set up lint + Documents.jl in same way it is defined in freshly started projects
- add lint + doctest to after_success so that build pass, these needs to be fixed later
- build is failing on nightly (0.7) but it's ok for release (0.5.2)
- Documenter.jl supports doctests, so this closes least #23
- build system is now on Travis-CI completely, so this closes also #68

docs/mkdocs.yml

@@ -0,0 +1,26 @@
+site_name: JuliaFEM.jl
+repo_url: https://github.com/JuliaFEM/JuliaFEM.jl
+site_description: Finite Element Method solver
+site_author: ahojukka5
+
+theme: readthedocs
+
+extra_css:
+    - assets/Documenter.css
+
+extra_javascript:
+    - https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML
+    - assets/mathjaxhelper.js
+
+markdown_extensions:
+    - extra
+    - tables
+    - fenced_code
+    - footnotes
+    - mdx_math:
+        enable_dollar_delimiter: True
+
+docs_dir: 'build'
+
+pages:
+    - Home: index.md