Get channel units for outlier removal

[macedo22]

When running gwdetchar-lasso-correlation, I found that some channels' TimeSeries.value held an array of floats, while others held an array of astropy quantity objects (astropy.units.Quantity). This change ensures that, when performing outlier removal, any possible Quantity units are preserved so that they can be successfully reassigned with their spline values.

[coveralls]

Pull Request Test Coverage Report for Build 252

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 40.0%

---

Totals
Change from base Build 251:	0.0%
Covered Lines:	428
Relevant Lines:	1070

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 252

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 40.0%

---

Totals
Change from base Build 251:	0.0%
Covered Lines:	428
Relevant Lines:	1070

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 252

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 40.0%

---

Totals
Change from base Build 251:	0.0%
Covered Lines:	428
Relevant Lines:	1070

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 252

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 40.0%

---

Totals
Change from base Build 251:	0.0%
Covered Lines:	428
Relevant Lines:	1070

---

💛 - Coveralls

[duncanmmacleod]

LGTM