Merge branch 'travis-fix'
Merge branch 'improve-Example'
Merge branch 'ben181231-master'
move "magic numbers" (tags numbers) to enum to avoid errors.
fix types casting and modern syntax
add one more tag to enum
Add 2 more tag-enums
move enum to .m file
Rename enums to simplify code review.
fix type missmatch
able to customize text on no data label
add pod spec
Merge branch 'master' into pr/90
Merge pull request #97 from Boris-Em/pr/90

Pr/90 - Various syntax changes / code improvement
Merge pull request #93 from sbhhbs/master

able to customize text on no data label
Add gradient properties to BEMLine and BEMSimpleLineGraphView classes
Rename existing unused gradient property of BEMLine to avoid confusion
Fill gradient in BEMLine when properties are set
Add example usage
Merge pull request #98 from kattrali/fill-gradients

Add ability to fill the top and/or bottom of a graph with a gradient