Fixed #155 Fixed bad implement, bad data structure CircularBuffer

fixed issue #155 improve data struct:

Pop now work like a stack (throw InvalidOperationException when pop an empty CircularBuffer)
No extra item in the inner array
Clear array instead of create anew
Fixed bad implement of IEnumerable (incorrect GetEnumerator, Contains, Remove)

[x] An issue was first created before opening this pull request
[x] The new code follows the contribution guidelines
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] I have made corresponding changes to the documentation
[x] My changes generate no new warnings
[x] I have added tests to ensure that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes

aalhour / C-Sharp-Algorithms