add pip version in yml

environment.yml

@@ -5,7 +5,7 @@ channels:
   - defaults
 dependencies:
   - python=2.7.13
-  - pip
+  - pip=18.1
   - conda-forge::scipy=1.0.1
   - conda-forge::numpy=1.9.3
   - conda-forge::r-markdown=0.8
@@ -13,7 +13,7 @@ dependencies:
   - bioconda::pysam=0.14.1
   - cooler=0.8.3
   - bowtie2=2.3.5
-  - samtools=1.9
+  - samtools=1.7
   - multiqc=1.6
   - pip:
     - iced==0.4.2
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