Findpeaks

* Fix for showing plots when using the command line.

* Fix in naming plot_peristance -> plot_persistance
* wget functionality replaced by request (thanks to bcbnz!)
* Catch error if mesh plot is used on 1D vector
* Update docs and examples
* Some cleaning

* small fixes

* code-refactored
* more errors and warnings captured
* persistence output improved
* sphinx pages created

Huge update!

* topology method implemented for 1D
* Persistance scores avaiable
* output is structured in a dataframe
* denoising (filtering) methods implemented such as lee, kuan, frost, median, mean, bilateral, fastnl
* plotting is possible for separate methods (topology, peakdetect)
* code is refactored
* code is cleaned
* docstrings added
* examples added

* exclude opencv from the default installation.
* small fixes