Updated dependencies.
Adding built gems to .gitignore.
Tracker operations now work with pre-selecting branches.

This makes the usage of tracker much more convenient.
Add operation to search for branches.
Fixed log ancestry and limit bugs.

- For my purposes I want the log to behave like its using the git-log
  option `--ancestry-path`;
- There is a default 30 limit to the log operation in the library,
  I needed to circumvent that.
Initial CLI interface for ahead/behind analysis.

Probably most of the code should be refactored into its own components
but at least the script is now usable for analysis.

Example output:
```
$ git log --oneline --graph --all --decorate
* bb62ee6 (HEAD, master) m3
*   5ab3f01 Merge branch 'r'
|\
* | 23e7058 m2
* | b4c12ca m1
| | * 08e7339 (r) r3
| |/
| * af75469 r2
| * de14754 1
|/
* 6530d98 first

$ gitra
---- Analyzing branches in relation to master ----
Analysing 2 branches: ..
master merged
     r 1 ahead (unmerged), (but 2 behind)

$ gitra r
---- Analyzing branches in relation to r ----
Analysing 2 branches: ..
     r merged
master 2 ahead (unmerged), (but 1 behind)
```