Add small dataset

data/random-15.txt

+# nbsegments 15 bbox -9995.9022086113691 -9909.3401059508324 8088.3203446865082 8589.2581567168236
+# mean_length: 11585.057426160329 (min: 3124.0921579058122   max: 18774.018223305964)
+3825.0240124762058 -5542.813939973712 4055.4712992161512 -1969.6665275841951
+-9921.2628602981567 -1987.4578900635242 -9627.0004007965326 3759.6752215176821
+-5491.0673759877682 -3754.9506314098835 -3639.0245705842972 7858.289573341608
+-9475.0122632831335 -9708.8304627686739 -6060.2445155382156 7031.2097296118736
+4562.2487179934978 1231.0688477009535 7675.4742302000523 970.72537988424301
+-4113.8386819511652 -9909.3401059508324 -3552.5823850184679 5389.1018778085709
+-8551.6668949276209 -7718.725772574544 -6541.2398148328066 8589.2581567168236
+-7397.8124558925629 -5508.4241461008787 7223.4569396823645 -9193.6955321580172
+-9995.9022086113691 -3541.4703283458948 896.72479778528214 -6882.5068790465593
+-9534.0603031218052 -1006.5399296581745 8088.3203446865082 5467.6751233637333
+-3715.4102418571711 6502.3933351039886 -2337.3466264456511 -759.6785482019186
+-8865.6509760767221 -7541.805524379015 1482.9017128795385 2012.1507439762354
+-9538.5510660707951 -418.27025823295116 707.42038078606129 7693.9730998128653
+-6647.0073908567429 -3400.8201211690903 5435.1287148892879 5335.5545457452536
+-5919.740553945303 4308.9899607002735 59.42080169916153 3519.6488443762064