Merge branch 'release/0.0.50' into develop
src: add instance method 'maxCoeff()'
test: add instance method 'maxCoeff()' testings

fix the description of ‘mean()’ testings
lint: add some files for linting pass
readme: add instance method 'maxCoeff()' api

improve some examples
npm: 0.0.50 -> 0.0.51
Merge branch 'release/0.0.51'