Eventio

* Several optimizations result in roughly 5 - 10% faster reading of simtel files
* `EventIOFile` and `EventIOObject` act as true iterators now (do not reset int `__iter__`)
* Removed the hotfix for the memory leak for zstd files, as this was fixed upstream in version 0.11.1

Merged PRs:

* Merge pull request 177 from cta-observatory/update_readme
* Merge pull request 174 from cta-observatory/fix_iterators
* Merge pull request 176 from cta-observatory/remove_zstd_hotfix
* Merge pull request 175 from cta-observatory/gitignore
* Merge pull request 172 from cta-observatory/reorder_ifs
* Merge pull request 171 from cta-observatory/no_init_parsing

* Better string representation of three iact objects
* fix seeking 0 bytes for zstd files

Monkey patch for zstandard memory leak, see 168

Add `tell` method to `PipeWrapper` to make it a valid file object

* Use gzip subprocess instead of gzip module by default, speeds up reading gz files by ~20%
* Remove unnecessary logging call in reading function, ~ 5% speed up
* Use explicit types from stdint.h for cython code to improve readability

* Do not read timestamp of `History*`, in `__init__`. These objects do no longer have
a timestamp member, but their `parse` methods return a tuple of `timestamp, content`.

* Refactor `iact.ArrayOffsets` to use the version header field instead of guessing the number of columns.

* Improve printing of objects (`__repr__` shows Low-Level eventio info, `__str__` shows higher level object info, improved printing utils)