Fix lib import; now works when invoking from sbin dir

Avoids dirname and two subshells
Avoid find and sed for listing commands
Convert spec_help to printf and make colors portable
Create FSExists function.

Comes with tests
Check if pool/fs exists when creating snapshots

Removes a grep call as well.

Two integrative tests disabled. Should be reused when we have a proper
test environment in which we can create and destroy filesystems and
snapshots.
Spelling fix
Merge pull request #41 from Alexqw/printf

Convert spec_help to printf and make colors portable
Merge pull request #40 from Alexqw/more_small_fixes

More small fixes
Merge pull request #35 from Alexqw/create_check

Check if pool/fs exists when creating snapshots
Switch to the BSD-3-Clause license.

See issue #44. Fixes #44.
Merge pull request #45 from Alexqw/bsd3clause

Switch to the BSD-3-Clause license.
Rename from zfSnap to zfsnap.

Fixes #46
Update all links to new location/name
Add -P back to `destroy`
Create TrimToDate function

Comes with tests.

Removes one sed call
Create TrimToTTL function

Comes with tests.

This unfixes bug fix 2) in 5d1c600279f6c9878aeb1194fc72088638a4362d
but it will be refixed again in a later patch.
Create TrimToSnapshotName function

Comes with tests
Create TrimToPrefix Function

Comes with tests.

Will be used by ValidSnapshotName in a later patch
Create ValidPrefix function

Comes with tests.

Will be used in ValidSnapshotName in a later commit.
Create TrimToFileSystem function

Will be used in a later commit.